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I ns t i t ut eo fMa na g e me nt & Te c hni c a lSt udi e s

I NTRODUCTI ONOFCOMPUTERS

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Di p l o mai nc o mp u t e rAp p l i c a t i o n www. i mt s i ns t i t ut e . c om


IMTS (ISO 9001-2008 Internationally Certified) DBA-INTRODUCTION OF COMPUTERS

INTRODUCTION OF COMUTERS

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COMPUTER PERIPHERALS AND MAINTENANCE

CONTENTS:

Unit – I 01-40 Introduction – PC – PC History – Fundamentals of Computer architecture Hardware devices, memory – types of memory – processor – Mother board & Bus form factors.

Unit – II 41-49 Peripherals – history of computer devices – keyboard – mouse – monitor – types of monitor – joystick – OMR – OCR – Barcode reader – Game controller – Touch screen – scanner – digital camera – wed camera and usage – Memory devices.

Unit – III 50-68 Printer – types of printers – Plotter – Multimedia devices – Sound card – Audio output devices – Optical Devices – CD/DVC drive and writer – Floppy and Floppy – device driver files.

Unit – IV 69-88 System Maintenance – Maintenance tools- Hand tool – soldering and de – soldering tools – meters – logic pulser – Memory maintenance – formatting – partition – fragmentation.

Unit – V 89-103 System power maintenance- SMPS – power protector’s power back up – UPS – inverter – Active and Preventive Maintenance systems – system tools – Checking and repairing.

UNIT QUESTIONS

104-107

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UNIT - I INTRODUCTION Computer is the most powerful tool man has ever created. Computers have made a great impact on our every day life. Their presence if felt at almost every working place viz. homes, schools, colleges, offices, industries, hospitals, banks, retail stores, railways, research and design organizations and so on. Computers, large and small, are used nowadays by all kinds of people or a variety of tasks in a modern and ind society.

Earlier computers were used for complex computations and used by only scientists and engineers. They were very costly and hence only large organizations could afford them. The technological breakthrough in design and fabrication of semiconductor devices had made now possible to manufacture powerful microcomputers which are within the reach of small organizations and even individuals. These computers being very fast can be used not only for computation but also to store and retrieve information, to control certain processes and machines, to measure and display certain physical and electrical quantities and so forth. DIGITAL AND ANALOG COMPUTERS Computers which are in use today are digital computers. They manipulate numbers. They operate on binary digits 0 and 1 They understand information composed of only 0s and 1s. In the case of alphabetic information, the alphabets are coded in binary digits. A binary digit is called bit. A group of 8 bits is called byte. They do not operate on analog quantities directly.

EVOLUTION OF DIGITAL COMPUTERS Electric computers using valves appeared in 1940s. The successful general purpose mechanical computers were developed in 1930s. Before 1930 mechanical calculators were built for automatic addition, subtraction, multiplication and division. A calculator is not a programmable device. Calculations are performed using step by step technique. The user does not prepare program for his calculation. A computer is a programmable machine. A program is to be prepared to solve a problem.

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The Mechanical Era A popular mechanical calculator was developed in 1642 by the great French philosopher and scientist Blaise Pascal. His machine was capable of performing addition and subtraction automatically. Around 1671 Pascal’s machine was extended to perform multiplication and division automatically by German philosopher and scientist Gottfried Leibniz. In 1823, Charles Babbage tried to build a mechanical computing machine capable of performing automatic multi-step calculations. He named his machine a difference engine. In 1823s Charles Babbage conceived of a much more powerful mechanical computer. He called this machine an analytical engine. This machine was designed to perform any mathematical calculation automatically. It contained all the essential components of a modern digital computer. In the late nineteenth century punched cards were commercially used. Herman Hollerith was the inventor of punched-card tabulating machine. The major application of his machine came about in the 1890 United States Census. The Electronic Era The first popular general purpose electronic digital computer was the ENIAC (Electronic Numerical integrator and Calculator). It was developed at the University of Pennsylvania under the guidance of John W.Mauchly and J.Presper Eckert. John Von Neumann was the consultant of the ENIAC project. It was a very large machine weighing about 30 tons and containing about 18000 vacuum tubes. The ENIAC designers, most notably John von Neumann, gave an idea to use a high-speed memory to store both program as well as data during program execution. This idea is known as stored program concept and was first published by Neumann for a new computer EDVAC (Electronic Discrete Variable Automatic Calculator) in 1945. The transistor was invented in 1948 at AT & T Bell Laboratories. In the 1950s the engineers started using transistors in place of vacuum tubes to construct computers. One of the earliest computers using transistor was TX-O. It was an experimental computer built at the Massachusetts Institute of Technology’s Lincoln Laboratories. It started operation in 1953. Commercial computers using transistors were constructed in the late 1950s and early 1960s by

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many companies. For example. IBM introduced a large computer, the 7090, for scientific applications. It was a transistorized version of the IBM 709, a vacuum tube computer. PERSONAL COMPUTER BACKGROUND Many discoveries and inventions have contributed to the development of the machine known today as the personal computer. Examining a few important developmental landmarks can help bring the whole picture into focus.

PERSONAL COMPUTING HISTORY A modern digital computer is largely a collection of electronic switches. These switches are used to represent, as well as control, the routing of data elements called binary digits (bits). Because of the on or off nature of the binary information and signal routing used by the computer, an efficient electronic switch was required. The first electronic computers used vacuum tubes as switches, and although the tubes worked, they had many problems. The tube was inefficient as a switch. It consumed a great deal of electrical power and gave off enormous heat-a significant problem in the earlier systems. Tubes were notoriously unreliable also; one failed every two hours or so in the larger systems . The invention of the transistor, or semiconductor, was one of the most important developments leading to the personal computer revolution. The transistor was invented in 1948 by John Bardeen, Walter Brattain, and William Shockley (engineers at Bell Labocatories).

The

transistor, essentially a solid-state electronic switch, replaced the much less suitable vacuum tube. Because the transistor consumed significantly less power, a computer system built with transistors was much smaller, faster, and more efficient than a computer system built with vacuum tubes. The conversion to transistors began a trend toward miniaturization that continues this day. Today’s small laptop (or palmtop) PC systems, which run on batteries, have more computer power than many earlier systems that all filled rooms and consumed huge amounts of electrical power.

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OVERVIEW OF SYSTEM FEATURES AND COMPONENTS Types of Systems

Many types of IBM and compatible systems are on the market today. Most systems are similar to one another, but a few important differences in system architecture have become more apparent as operating environments such as Window and OS/2 have increased In popularity. Operating systems such as OS/2 l. x require at least a 286 CPU platform on which to run. OS/2 2,x requires at least a 386 CPU. Environments such as, Windows offer different capabilities and operating modes based on the capabilities of the hardware platform on which you run it. Knowing and understanding the differences in these hardware platforms will enable you to plan, install, and utilize modern operating systems and applications to use the hardware optimally.

All IBM and compatible systems can be broken down into two basic system types, or classes, of hardware: PC/XT class systems AT class systems

The term PC stands for Personal Computer, of course, while XT stands for extended. The XT is basically a PC system that includes a hard disk for storage in addition to the floppy drive(s) found in the normal PC system. These systems have an 8-bit 8088 processor and an 8-bit Industry Standard Architecture (ISA) Bus for system expansion. The bus is the name given to expansion slots where additional plug-In circuit boards can be installed. The 8 bit designation comes from the fact that the ISA Bus found in the PC/XT class systems can only send or receive 8-bits of data in a single cycle. The data in an 8-bit -bus is sent along eight wires-simultaneously in parallel. More advanced systems are said to be AT class which indicates that they follow certain standards first, set forth in the IBM AT system, AT stands for Advanced Technology, which is the designation IBM applied to systems that first included more advanced 16-bit (and later 32and 64-bit) processors and expansion slots. AT class systems must have any processor

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compatible with the Intel 286 or higher processors (including the 386, 486, and Pentium processors) and must have a 16-bit or greater expansion slot system. The bus architecture is central to AT compatibility; PC/XT class systems with upgraded processor boards that do not include the 16-bit or greater expansion bus do not qualify as true AT systems. The-first AT systems have a 16-bit version of she ISA Bus, which is an extension of the original 8-bit ISA Bus found in the PC/XT class systems. Eventually a number of. expansion slot or bus designs were developed for AT class systems, including those listed here: 16/32-bit ISA Bus 16/32-bit Enhanced ISA (EISA) Bus 16/32-bit PS/2 Micro Channel Architecture (MCA) Bus 16-bit Personal Computer Memory Card International Association (PCMCIA) Bus 16/32/64-bit Video Local (VL) Bus 32/64-bit Peripheral-Component Interconnect (PCI) Bus

A system will any of these types of expansion slots is by definition an AT class system, regardless of the actual processor used. AT-type systems with 386 or higher processors have special capabilities not found in the first generation of 286-based ATs. The 386 and higher systems have distinct capabilities regarding memory addressing, memory management, and possible 32-bit-wide access to data. Most systems with 386DX or higher chips have 32-bit slots to take full advantage of the 32-bit data-transfer capabilities.

The ISA and MCA architectures were developed by IBM and copied by other manufacturers for use in compatible systems. Other expansion bus designs were independently derived by other companies. For years the ISA Bus dominated the IBM-compatible marketplace. When the 32-bit 386DX processor debuted, however, there arose a need for a 32-bit expansion slot design to match. IBM took the high road and developed the Micro Channel Architecture Bus, which has outstanding technical capabilities compared to the previous ISA designs. Unfortunately, IBM has had a difficult time marketing the MCA Bus due to problems with the high cost of manufacturing MCA motherboards and adapter cards, as well as the perceived notion that MCA is proprietary. Although it is not, IBM has not succeeded in marketing it as the

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new bus of choice, and it has remained largely a feature of IBM, systems only. The rest of the marketplace has for the most part ignored MCA, although a few companies have produced MCA-compatible systems and many companies reduce MCA expansion adapters:

Compaq, for example, was the primary architect of the Extended Industry Standard Architecture Bus. Realizing the difficulty IBM had in marketing its new MCA Bus, Compaq decided that the best approach would be to give the bus design away rather than to keep it as a Compaq-only feature. They feared a repeat of what IBM was going through in trying to get the MCA Bus accepted throughout the Industry. After all, how many companies would market expansion cards for a new bus unique to Compaq systems? Compaq derided that others should share in their new design, and they contacted a number of other system manufacturers to see if they were interested in participating. This led to the EISA consortium, which in September 1988 debuted the Compaq-designed expansion bus: Extended Industry Standard Architecture (EISA). The system is a 32-bit slot for use with 386DX or higher systems:

Speculators said that EISA was developed to circumvent the royalties IBM charges competitors who use the ISA or MCA slot design in their-systems. This speculation was false because EISA is an extension of the IBM-developed ISA Bus, and manufacturers of EISA systems must pay IBM the same licensing fee, as do manufacturers of ISA or MCA systems. EISA was developed not to circumvent licensing fees, but to show technological leadership and to enable Compaq and other companies to have some design freedom and control over their systems. Whether EISA, an alternative to the IBM-designed MCA, becomes a useful standard depends on the popularity of systems that use the slot.

Unfortunately, EISA never achieved great popularity and sold in far smaller numbers than did MCA systems. There are fewer EISA expansion adapters than MCA adapters, as well. This failure in the marketplace occurred for several reasons. One is the high cost of integrating the EISA Bus into a system. The special EISA Bus controller chips add several hundred dollars to the cost of a motherboard

, having EISA slots onboard can double the cost of the

motherboard. Another reason for the relative failure of EISA was the fact that the performance it

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offered was actually greater than most peripherals it could be connected to! This Incompatibility in performance was also true for MCA. The available hard disks and other peripherals could not transfer data as fast as the 16-bit ISA Bus could handle, so why use EISA, a still faster bus? Memory had already found its way off the standard bus and was normally installed directly on the motherboard via SIMMs (Single In-line Memory Modules). EISA complicated system installation and configuration whenever Standard ISA boards were mixed with EISA boards. The standard ISA boards could not be controlled by the EISA configuration program required to configure the jumper and switchless EISA cards. In the years following EISA's introduction. It found a niche in high-end server systems because of the bus's Increased bandwidth. For standard workstations, however, the EISA Bus has been superseded by VL-Bus and PCI.

The newest trend in expansion slots is the local bus. This type of bus is connected closely or directly to the processor. A problem with ISA and EISA is that the bus speed was locked In at 8.33 MHz, which was far slower than the processors. What was needed were expansion slots that could talk directly to the processor, at processor A problem with ISA and EISA Is that the bus speed was speed using all the bits the processor could handle. The first of the local buses to achieve so named because it actually was designed for video adapters. The VL Bus was created initially by NEC Corporation, who sought to include it in their systems to allow much faster video adapter functionality. Because NEC Corporation saw strength in numbers, they decided to give away the VL-Bus and other standards. The inexpensive design and high performance of the VL-Bus made it a popular addition to the ISA Bus and even to some EISA systems. VL-Bus was defined as an extension connector to the ISA or EISA Bus and could be found only in systems with those buses.

Peripheral Component interconnect Bus was created by Intel to be a new generation bus, offering local bus performance while also offering processor Independence and multiple processor capabilities. Like so many of the other bus creators, Intel formed an independent organization to make the PCI Bus an Industry standard in which all could participate. The PCI Committee was formed to administer this new bus and to control its destiny. Due to the superior design and performance of PCI, it has rapidly become the bus of choice in the highest

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performance systems. Over the next few years, we will probably see PCI unseat the ISA Bus and become the dominant bus architecture. You usually can identify PC and XT types of systems by their Intel-design 8038 or 8086 processors; many possibilities are available, however. Some systems have the NEC V-20 or V-30 processors, but these processors are functionally identical to the Intel chips. A few PC or XT systems have a 286 or 386 processor for increased performance.

These systems have only 8-bit slots of the same system-bus

design featured in the original IBM PC. The design of these slots includes only half the total DMA and hardware interrupts of a true AT design, which severely limits the use of expansion slots by different adapter boards that require the use of these resources. This type of system can run most software that runs under MS-DOS, but is limited in more advanced operating systems such as OS/2. This type of system cannot run OS/2 or any software designed to run under OS/2, nor can it run Windows 3.1 or greater. These systems also cannot have more than I megabyte of processor-addressable memory, of which only 640K is available for user programs and data.

You usually can identify AT systems by their Intel-design 286, 386, or higher processors. Some AT systems differ in the types of slots included on the main system board, the earlier standard called for 8/16-bit ISA slots compatible with the original IBM PC and AT�. Other standards such as EISA, MCA, PCMCIA, VL-Bus, and PCI also would be found only in AT class systems. Most of these systems today would use 486 Pentium processors.

PC systems usually have double-density (DD) floppy controllers, out AT systems must have a controller capable of high-density (HD) and double-density operation. Almost all current systems also have a controller capable of extra-high density (ED). These systems can run the 2.88M floppy drive. Because of the different controller types, the boot drive on a PC system must be the DD, 5 1/4-inch 360K or 3 1/2-inch 720K drives, but the AT needs the 5 1/4-tnch 1.2M or the 3 1/2-Inch 1.44M or 2.88M drives for proper operation. You can use a doubledensity disk drive as the boot drive in an AT system; the problem is that your boot drive is supposed to be a high-density drive. Many applications that run on only AT-type systems are packaged on high-density disks. The OS/2 operating system, for example, is packaged on high-

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density disks and cannot be loaded from double-density disks. The capability to boot and run OS/2 is a basic AT-compatibility test.

A subtle difference between PC/XT and AT systems is in the keyboard interface. AT systems use a bi-directional keyboard interface with an Intel 8042 processor “running the show�. This processor has ROM built-in and can be considered a part of the total system ROM package. The PC/XT systems used an 8255 Programmable Peripheral Interface (PPI) chip, which supports only a unidirectional interface. A keyboard can be configured to work with only one of the interface designs. With many keyboards, you can alter the way the keyboard Interfaces by flipping a switch on the bottom of the keyboard. Others, such as IBM's Enhanced 101-key keyboard, detect which type of system they are plugged into and switch automatically. The older XT and AT keyboards work with only the type of system for which they were designed. The AT architecture uses: CMOS memory and a real-time clock; the PC-type systems usually don't. (An exception .is the PS/2 Model 30, which has a real-time clock even though it is an XT class system.) A real-time clock is the built-in clock implemented by a special CMOS memory chip on the motherboard in an AT system. You can have a clock added on some expansion adapters in a PC system, but DOS does not recognize the clock un-less a special program is run first. The CMOS memory in the AT system also stores the '/stem's basic configuration. On a PC- or XT-type system, all these basic configuration options (such as the amount of installed memory, the number and types of floppy drives and hard disks, and the type of video adapter) are set by using switches and jumpers on ;he motherboard and various adapters.

The serial-port control chip, Universal Asynchronous Receiver/Transmitter (UART), is a National Semiconductor 82SOB for the PC-type systems; AT systems use the newer NS 16450 or 16550A chips. Because these chips differ in subtle ways, the BIOS software must be designed for a specific chip. In the AT BIOS, designed for the 16450 and 16550A chips, using the older 82508 chip can result In strange problems, such as lost characters at high transmission speeds.

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Some differences (such as the expansion slots, the hardware interrupts, and the DMA channel availability) are absolute. Other differences, such as which processors are supported, are less absolute. The AT systems, however, must use the 286 or higher; the PC systems can use the entire Intel family of chips, from the 8086 on up. Other parameters are less absolute. Your own system might not follow the true standard properly. If your system does not follow all criteria listed for it, especially if it is an AT-type system, you can expect compatibility and operational problems.

COMPUTER GENERATIONS First Generation (1946-1954) The digital computers using electronic valves (vacuum tubes) are known as firstgeneration computers. Some examples of the first-generation computers are: IBM 700 seriesIBM 701, IBM 704, IBM 709, EDVAC and INIVAC. The first-generation computers usually used vacuum tubes as CPU components.

The first generation computers used assembly language for programming. They used fixed-point arithmetic.

Second Generation (1955-1964) The second-generation computers used transistors for CPU components and ferrite cores for main memory, and magnetic such as FORTAN (1956) ALGOL (1960) and COBOL (1960) for programming.

Third Generation (1965-1974) In the beginning third generation computers used magnetic core memory, but later on semiconductor memories (RAMs and ROMs) were used. Semiconductor memories were LSI chips. Magnetic disks. drums and tapes were used as secondary memories. Cache memory was also incorporated in the computers of third generation. Microprogramming. Parallel processing (pipelining, multiprocessor system. etc) multiprocessing, parallel processing

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(pipelining, multiprocessor system).etc. were introduced. The concept of virtual memory was also introduced. The example of third generation computers are: IBM/370 series (1970). CDC 7600 (1969). PDP 11 (16-but minicomputer, 1970), CDC’s CYBER – 175 and STAR – 100. etc.

Fourth Generation (1975-up till now) The fourth – generation computers use VLSI chips for both CPU and memory. A CPU consists of one or more microprocessors.

Many improvements have been made in speed, memory size and packing density of ICs. Many components such as CPU, and several I/O devices are being packed into a single chip. Example of fourth-generation computers are: CRAY Y-MPC (1992) CRAY 2 (1985), CRAY Y-MP (1988), IBM 3090/600 (1988), IBM ES/9000 (latest series), VAX 8842 (1988), IBM AS/400/460 (1988), IBM PS/2/50 (1987), IBM PS/2 model 80, WIPRO LANDMARK 860, S68030 V,HCL Magnum with 68030 CPU, Magnum 040 series (68040 CPU), HP 9000 series 800; HP 3000 Model 870S/400, HP 3000 Model 870S/300, etc.

Fifth Generation The fifth-generation computers are under development stage, Japan and USA have under taken projects to design and develop such computers. These computers will use USLI (ultra-large-scale integration) chips. ULSI chips contain millions of components into a single IC. Such computers will use intelligence programming, knowledge-based problem solving techniques, high performance multiprocessor system and improved human-machine interfaces.

MAJOR COMPONENTS OF A DIGITAL COMPUTER The major components of a digital computer are: CPU (central processing unit), memory, input device and output device. The input and output devices are also known as peripherals. Fig. 1.1 shows a schematic diagram of a digital computer.

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CPU The CPU is the brain of a computer. Its primary function is to execute programs. Beside executing programs, the CPU also controls the operation of all other components such as memory, input and output devices. Under its control, programs and data are stored in the memory and displayed on the CRT screen or printed on the printer. (i) Arithmetic and Logic Unit (ALU) The function of an ALU is to perform arithmetic and logic relations such as addition, subtraction, multiplication, and division; AND. OR, NOT (complement an EXCLUSIVE OR operation. (ii) Timing and Control Unit The timing and control unit generates timing and control signals necessary for the execution of instructions. It provides status, control and timing signals necessary for the operation of other parts of the CPU, memory and I/O devices. It controls the entire operation of a computer. It is actually the control section of the CPU, which acts as the brain of a computer.

(iii) Accumulator, General and Special Purpose Registers The accumulator is a register which holds one of the operands prior to the execution of an instruction and receives result of the most arithmetic and logical operations. It is the most frequently used register. Memory The function of the memory is to store information. It stores program, data, results or any other kind of information. Two or three levels of memories such as main memory, secondary memory the main memory (or primary memory) is a fast memory. It stores programs

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along with data, which are to be executed. It also stores necessary programs of system software, which are required to execute the user's program. The main memory is directly addressed by the CPU. Semiconductor memories, RAMs are used as main memory It possesses random access property, and has smaller access time, 80-100 ns (nanosecond). Secondary (or auxiliary) memory stores operating system, data files, compilers, assemblers, application programs, etc. The CPU does not read information (residing in the secondary memory) directly from the secondary memory. The programs and data (residing in secondary memory), if needed by CPU, are first transferred from the secondary memory to the primary memory. Then the CPU reads them from the primary memory. The results are also stored in the secondary memory. The secondary memory is a mass storage memory. It is slow but cheap. It is a permanent memory while the main memory (RAM) is volatile memory. The capacity of the main memory is comparatively much smaller than that of the secondary because of its high cost.

The cache memory is placed in between the CPU and the main memory. It is much faster than the main memory; access time 15 -25 ns. It stores instructions and data which are to be immediately executed. It is much costlier than the main memory. Hence, from cost consideration its capacity is kept much less than that of the main memory.

Semiconductor Memory Semiconductor memories are of two types: RAM (random access memory) and ROM (read only memory). RAM is a read/write memory. Information can be written into and read from a RAM. It is a volatile memory. It stores information so long as power supply is on. When power supply goes off or interrupted the stored information in the RAM is lost. ROM is a permanent type memory. Its contents are not lost when power supply goes off. The user cannot write into a ROM. Its contents are decided by the manufacturer and written at the time of manufacture. Magnetic Memory Magnetic memories are nonvolatile memory. They store information permanently. They are slower than semiconductor memory. The commonly used magnetic memories are of three

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types: hard disks, floppy disks and tapes. These devices are bulk storage devices. They are used to store information at a lower cost compared to semiconductor devices. These are not static devices. They are rotated while reading or writing information.

Input Devices Information is entered into a computer through input devices. An input device converts input information into suitable binary form acceptable to a computer. The commonly used input device is a keyboard. Several input devices which do not require typing of input information have been developed, for, example, mouse, joystick, light pen, graphic tablet, touch screen and trackballs.

Self Assessment Questions

1. PC means__________________ 2. What is ALU? 3. Input devices are ____________ __________ __________

Answer: 1. Personal Computer 2. Arithmetic and Logic unit 3. Key board, Mouse, Joy Stick

Output Devices The output devices receive results and other information from the computer and provide them to users. The computer sends information to an output device in the binary form. An output device converts it into a suitable form convenient to users such as printed form, display on a screen, voice' output,

Buses Memory and I/O devices are connected to the CPU through a group of lines called a bus. These lines are meant to carry information. There are three types of buses: address bus, data bus and control bus. An address bus carries the address of a memory location or an I/O

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device that the CPU wants to access. The address bus is unidirectional. The data and control buses are bidirectional because the data can flow in either direction; from CPU to memory (or I/O device) or from memory (or I/O device) to the CPU.

Personal Computer (PC) From cost and performance point of view personal computers are classified as PC, PC/XT. PC/AT and super AT (or super micro). When we use the term PC in general literature to discuss certain features of personal computers, it means all categories of PCs. that is. PC. PC/XT. PC/AT and super micro. All categories of personal computers contain a CPU, RAM. ROM. CRT display, keyboard and secondary memory (hard/floppy disk). PC is the simplest and cheapest type of personal computer. Minicomputers Minicomputers are faster and more powerful than microcomputers. Their word length is 32 bits. The processing speed lies in the range 10-30 MIPS, Minicomputers are extensively used for payroll preparation, accounting and scientific computation. High-performance workstations with graphics input/output capability use minicomputers. applications in colleges, universities, research organizations, government organizations, industries and so on.

Mainframe Computers The mainframe computers are very powerful large general purpose computers. They are faster and more powerful than minicomputers. Their word length may be 48, 60 or 64 bits, memory capacity, 64-256 MB, processing speed, 30-100 MIPS. They are used where large amount of data are to be processed or very complex calculations are to be made, and these tasks are beyond the computing capacity of minicomputers. They are used in research organizations, large industries, large business and government organizations; banks and airline reservations where large database is required. Supercomputers Supercomputers are much faster and more powerful than mainframe computers. Their processing speed lies in the range of 400 MIPS-10,000 MIPS, word length 64-96 bit, memory capacity 256 M3 and more, A supercomputer contains a number of CPUs which operate in

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parallel to make it faster. They are used for massive data processing and solving very sophisticated problems. They are used for weather forecasting, weapons research and development, rocketing, in aerodynamics, seismology, atomic, nuclear and plasma physics.

Memory Memory is an essential component of a digital computer. It is a storing device. It stores programs, data, results etc. At present the following two kinds of memory are commonly used in modem computers: (i)

Semiconductor memory

(ii)

Magnetic memory

The semiconductor memory is faster, compact and lighter. It consumes less power. The semiconductor memory is a static device. There is no rotating part in it. The magnetic memory is slow compared to semiconductor memory. But it is cheaper than semiconductor memory. It is not a static device. It is either in the form of a rotating disk or tape.

MAIN MEMORY, SECONDARY MEMORY AND BACKUP MEMORY All computers except very small systems contain both semiconductor as well as magnetic memory. The semiconductor memory is employed as the main memory (or primary memory) of the computer. It stores programs and data which are currently needed by the CPU. The magnetic memory is used as secondary (or auxiliary) memory. The information which is not being currently processed resides in the secondary memory. The information which is needed by the CPU for current processing is transferred from the secondary memory to the main memory. The size of the main memory is comparatively much smaller than that of the secondary memory because of its high cost.

The secondary memory is employed for bulk storage (mass storage) of programs, data and other informations. It has much larger capacity than main memory. It stores system software, assemblers, compilers, useful packages, large data files etc. The secondary memory should not be of volatile nature. It must store information permanently. The magnetic memory

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has this property. It retains the information once stored in it. The magnetic memories such as hard disks and floppy disks are the most common secondary memories used in computers.

CACHE MEMORY The cache memory is placed in between the CPU and main memory. It is much raster than main memory. Its access time is much less compared to that of the main memory. The access time of a cache memory is 15-25 nanoseconds (ns) whereas that of the main memory is 80 ns. The cache memory is not accessible to users. It stores instructions and data which are to be immediately executed. It is used to reduce the average access time for address, instructions or data which are normally stored in the main memory. Thus the cache memory increases the operating speed of the system. But it is much costlier than main memory.

REAL (OR PHYSICAL) AND VIRTUAL MEMORY The real or physical memory is the actual main memory provided in the system. It is directly addressed by the CPU. The address of a location of the physical memory is called physical address.

The technique which allows a program to use main memory more than what a computer really has is known as virtual memory technique. It gives the programmers an illusion that they have main memory available more than what is physically provided in the computer. The entire program and its data are not placed in the main memory. Only the instructions and data which are to be currently executed are brought from the secondary memory into the main memory. The remaining part of the program resides in the secondary memory. When the part of the program which is in the main memory has been executed, it is sent back to the secondary memory.

SEMICONDUCTOR MEMORY Semiconductor memories are of two types: RAM (random access memory) and ROM (read only memory). The various kinds of RAMs and ROMs are as described below.

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RAM The read and write memory (R/W memory) of a computer is called RAM. The users can write information into RAM and read information from it. It is accessible to users. The user enters his program and data into RAM. It possesses random access property. In a random access memory any memory location can be accessed in a random manner without going through any other memory location. The access time is same for each memory location. RAM is a volatile memory. The information written into it is retained in it as long as the power supply is on. As soon as the power supply goes off (or interrupted) its stored information is lost. The programmer has to reload his program and data into the RAM when the power supply is resumed.

There are two important types of RAMs: static RAM and dynamic RAM. Static RAMs retain stored information only as long as (he power supply is on. But a dynamic RAM loses its stored information in a very short time (a few milliseconds) even though the power supply is on.

ROM ROM stands for “Road Only Memory�. It is nonvolatile memory, i.e. the information stored in it is not lost even if the power supply goes off. It is used for permanent storage of information. If also possesses random access property. ROMs are much cheaper compared to RAMs. The stored information can only be read from ROMs at the time of operation. Informati9on can not be written into a ROM by the users/programmers. The contents of ROMs are decided by the manufacturers. The contents are permanently stored in a ROM at the time of manufacture. PROM PROM is a programmable ROM. Its contents are decided by the user. The user can store permanent programs, data or any other kind of information in a PROM. A special equipment called PROM programmer is available for the programming of PROMs. With the help of PROM programmer the user stores his programs in a PROM. PROMs are once programmable, i.e. the user can write his information in a PROM only once. PROMs are more cost effective if small number of chips are to be produced to store certain fixed programs.

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EPROM An EPROM is an erasable PROM. The stored data in EPROMs can be erased by exposing it to high intensity short wave ultraviolet light for about 20 minutes. An UV source of 2537 A wavelength can be used for the purpose.

The technique of erasing contents is not easy and convenient because the EPROM 1C has to be removed from the computer for the exposure lo the ultraviolet light. When an EPROM is exposed lo ultraviolet light the entire data are erased. The user cannot erase the contents of certain selected memory locations. EPROMs are cheap, reliable and hence they arc widely used.

EEPROM (or E2ROM) EEPROM is an electrically erasable PROM. It is also known as EAPROM (Electrically Alterable PROM). The chip can be erased and reprogrammed on the hoard easily on a byte by byte basis. Either a single byte or the entire chip can be erased in one operation. It requires much shorter lime. a few milliseconds for erasing ;is compared to 10-20 minutes for EPROM.

MAGNETIC MEMORY The magnetic memories are permanent memory. They are not volatile. The following are the types of magnetic memory: (i) Floppy disks (ii) Hard disks (iii) Magnetic tapes

Floppy Disks Floppy disks are commonly used as secondary and backup memory in personal computers. They are also called diskettes. These disks are very thin and flexible and hence, they are called floppy. These are made of Mylar with a coating of magnetic material (iron oxide) on it. They are small, convenient and inexpensive. They are removable disks. A floppy disk is

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inserted into the computer when needed. If the same disk is to be used again and again, it can be kept inserted in the system. It is kept in a square protective cover made of thin plastic. The disk rotates freely in the protective cover (jacket). The most popular sizes of floppy disks are: 5.25 inches square and 3.5 inches square.

Working Principle A floppy disk is a surface device. The surface is divided into a number of concentric circles called tracks. Information is recorded on the tracks. Magnetic domains (or tiny magnetic spots) to represent 1 or 0 arc in the form of bars.

Hard Disks A hard disk is made of aluminium or other metals or metal alloys instead of plastic (i.e. thin flexible Mylar sheet). The disk is coated on both sides with magnetic material (iron-oxide). Unlike a floppy disk, a hard disk can not be inserted or removed from the hard disk drive unit. To increase the storing capacity several disks (or platters) are packed together and mounted on a common drive to form a disk pack as shown in Fig. 6.4. The term cyliner is usually used

It stores more information at faster rate compared to floppy disks. A hard disk is also divided into tracks and sectors. Most hard disks contain 17 sectors per track (the range may be 17 to 40 sectors per track). It can have 200 to over 1000 tracks per surface and bit density over 10,000 bits per inch of a track. The data transfer rate is 10 MB/sec.

The disks come in different sizes such as 3.5 inch, 5.25 inch and 8 inch. The larger disks are used in large computers, and the smaller disks in PCs and mini computers. Magnetic Tape It is a mass storage device. It is used as a backup storage. Floppy disks are also used as backup for hard disks. But difficulty with floppy disks is that a large number of floppies is required. For 10 MB hard disk 30 number of 360 KB. floppy disks are needed. Moreover, it is a slow and time consuming process. It is better to have a high speed tape system for hard disks

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backup. Only a few minutes are required to dump or load the entire contents of the hard disks to or from a single tape.

The magnetic tape is made up of plastic material (mylar) coated (only one side of the tape) with magnetic material. The standard tape is 0.5 inch wide and contains 9 tracks. It is coated with iron-oxide magnetizable material. The newer 0 5 inch tape contains 18 tracks and are coated with chromiumdioxide. The tapes of the newer system are contained in 4 x 5 inch cartidges. While the data density of a 9-tracks tape is 6,250 characters per inch, the data density of a 18-track tape is 38,000 characters per inch of the tape. The tape comes in a large reel. or a small cartridge or cassette.

OPTICAL DISKS Information is written to or read from an optical disk using laser beam. An optical disk has very high storing capacity, for example, a 5.25 inch optical disk stores 550 MB. Only one surface of an optical disk is used to store data. An optical disk is relatively inexpensive, and has a long life of at least 20 years. Its drives are inherently simple and inexpensive. As the read/write head does not touch the disk surface, there is no disk wear and no problem of head crash.

MAGNETIC BUBBLE MEMORY It is nonvolatile magnetic memory without any moving part. It semi random access and nondestructive readout property. It is a solid state static device available in 1C form. It has high reliability, high data density, raggedness, small size, light weight, limited power dissipation and long life (20 years or more). It can be used as a mass storage device in a computer. Its average access lime is 0.7 ms as compared to 40 ms rating of a fast hard disk. The main disadvantage is its slow data transfer rate, 1.6 MB per .second as compared to 5 MB or 10 MB/sec for a hard disk. It is very expensive. It is used in robots, machine tools and military applications where delicate rotating hard disk is not desirable. Intel has developed 1 MB and 4 MB bubble memory chips.

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Self assessment Questions 4. What is soft ware? 5. Two types of Software are ___________, ______________ 6. RAM stands for ___________________

Answer: 4. Set of Programs to run the Computer. 5. Application, System 6. Random Access memory.

I/O PROCESSOR I/O processor is a special purpose processor used exclusively to control input/output operations. It is also called peripheral processing unit (PPU). In programmed data transfer I/O devices are controlled directly by the CPU. In DMA data transfer the I/O devices have limited control over data transfer. An I/O processor has full control over I/O operations. An I/O processor is like a CPU. It has its own instruction set. But its instruction set is a restricted one compared to that of a CPU. It has a small and specialized instruction set mainly for I/O operations. An I/O processor is primarily a communication link between I/O devices and the main memory and hence the term channel is also used for I/O processor.

In a computer system with I/O processor the data-transfer instructions are not normally executed by the CPU. Such instructions are included in the I/O programs stored in the main memory. The I/O processor can fetch and execute these programs at the direction of the CPU. However, a small number of I/O instructions are executed by the CPU. These instructions permit the CPU to initiate and terminate the execution of I/O programs through I/O processor. Such instructions also test the status of the I/O system. An I/O processor is capable of supporting DMA data transfer. In a computer system if there are a few fast devices or a large number of slow devices, the CPU must give appreciable time for the execution of I/O programs. Consequently, the CPU gels less lime to perform its own task of data processing. An I/O

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processor relieves the CPU from the task of I/O operations and improves the overall performance of the system.

The CPU and I/O processor share a common memory as shown in Fig. 7.20 The memory contains separate programs to be executed by the CPU and the VO processor. It also contains a communication region IOCR used for passing messages between the, CPU and I/O processor. The CPU can place there the parameters of an I/O task such as the address of the I/O programs to be executed and the identity of the devices to be used. The CPU and VO processor can also communicate more directly through special control lines. The CPU can attract the attention of an I/O processor by activiting the ATTENTION line. For example, the attention of I/O processor can be drawn while executing an I/O instruction such as START I/O or TEST I/O.

7.13.1 Intel 8089 The 8089 is an 8/16 bit HMOS I/O processor. It is compatible with 8086 and 8088 processors. It contains a pair of DMA channels. Each channel can perform independent I/O operation. Besides usual address and data-count registers the DMA channels have their own program counters and other circuitry needed to execute its instruction set which is specialized for I/O operations. Its instruction set is quite distinct from that of the host CPU. The instruction set includes about 50 different instruction types. Its major instruction types are data-transfer instructions. These instructions move data or address between 8089's internal registers and its external memory-I/O bus. Its instructions are similar to those of a general-purpose CPU. A few are address type instructions. Very limited instructions are for data processing and program control. For example, the arithmetic instruction include only add, increment and decrement with unsigned or twos-complement fixed-point operands. There is no provision for overflow detection in signed arithmetic operations. The 8089 is capable of .executing two unrelated I/O programs concurrently.

The high speed DMA capability includes I/O to memory, memory to I/O, memory to memory and I/O to I/O data transfer. It permits mixed interface of 8-and 16-bit peripherals to 8

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and 16-bit processor busses. Its addressing capability is 1 MB. It can support local or remote I/O processing. It is packed in DIP 40-pin 1C. The communication between the CPU and IOP is made through messages prepared in shared memory. The CPU directs 8089 to execute a program by placing it in the 8089's memory space and/or directing 8089's attention to it by applying a hardware signal (called channel attention, CA) to the IOP. The communication from IOP to the. CPU is made via system interrupt if the CPU has enabled the interrupt for this purpose. The 8089 can store message in memory in connection with its status and the status of any peripherals.

Intel 82258 It is an advanced high performance 16-bit DMA coprocessor optimized for 80286 and 80186 families of microprocessors. It has 8 MB/sec. data transfer rate in 8 MHz 80286 system. It is compatible with 80386 CPU. It has on-chip bus interface for the whole 8086 family architecture, i.e. 8086, 80186, 80286, 8088 and 80188. It has 16 MB addressing capability and hence it can address the full 80286 CPU memory. It has 4 high speed independently programmable channels. Channel 3 can be used as a multiplexer channel having capability to support 32 subchannels. This flexibility permits one to use a single DMA channel to handle a large number of I/O devices of slow and medium speed. In addition to providing high speed DMA transfer, the 82258 takes I/O processing load from the CPU.

It has some advanced features which are not present in previous generations of DMA controllers. These are: multiplexer channel, command chaining and date chaining. The 82258 permits chaining of command blocks in the memory for any channel for sequential execution. The data chaining permits gathering and scattering of data blocks. It is possible to perform automatic, dynamic linking of the data blocks scattered in the memory. Each block of the data in a chain may be up to 64 KB. For more details see Intel's peripheral handbook. It is available in 68-pin-cerdip package. Its other features are: on the fly compare, translate and verify; automatic assembly and disassembly of data. programmable bus loading. 6 and 8 MHz speed selection, etc.

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UPI-452 The UPI-452 (universal peripheral interface) is a CHMOS programmable I/O processor. It is a general purpose slave I/O processor. Actually the UPI-452 is a slave microcontroller. It incorporates an 80C51 (a single-chip microcomputer) with double program and data memory, a slave interface which permits it to be connected directly to the host system bus as a peripheral, a FIFO buffer module, a two channel DMA controller, and a fifth I/O port. Fig. 7.21 shows the functional block diagram of UPI-452. Its main features include 256 x 8-bit internal RAM. 8-KB ROM/EPROM. two 16-bit timers/counters. Boolean processor, bit addressable RAM, 8 interrupt sources, programmable full duplex serial channel, 34 additional special function registers. 40 programmable I/O lines, 128-byte bidirectional FIFO slave interface, two DMA independent channels, 64K program memory space. 64K data memory space, 68-pin PGA and PLCC package. software compatible with the MCS-51 family of single-chip microcomputers etc.

The on-chip DMA controller permits high speed data transfer between any of the three writable memory spaces: internal data memory, external local expansion bus data memory and the special function register array. The special function register array is treated as a set of unique dedicated memory addresses which can he used as cither the source or destination address of a DMA transfer. Each DMA channel can be independently programmable. For this purpose there are dedicated special function registers for mode. source and destination addresses and byte count to be transferred. Upto 64 KB can be transferred in a single DMA operation. Each DMA channel may operate in either block mode or demand mode. In block mode of data transfer there are two techniques: burst mode or alternate cycle mode. In burst mode processor halls its execution and DMA data transfer lakes place. In alternate cycle mode DMA cycle and instruction cycle lake place alternately. The demand mode data transfer may be of two types: (i) FIFO or serial channel demand mode and (ii) external demand mode. In demand mode. a DMA data transfer takes place when it is demanded. Demand can be accepted from an external device (through external interrupt pins) or from either the serial channel or FIFO Hags. In these cases the DMA data transfer can be synchronized to an external device, the FIFO or the serial port.

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UPI-41,42 These are general purpose universal peripheral interfaces to control I/O devices. They are essentially slave microcontrollers with interface included on the chip. They contain microcontrollers 8041 AH. 8042 AH, 8741 AH or 8742 AH. The UPI 41 operates at 6 MHz and UPI-42 at 12 MHz. They are, compatible with all Intel and most other microprocessors. They contain 8-bit CPU plus ROM/EPROM. RAM, I/O Timer/Counter and clock with DMA, interrupt or polled operation support in a single package. Upi-42 has 8042 AH or 8742 AH microcontroller. UPI-41 contains 8041 AH or 8741 AH microcontroller. The ROM/EPROM in different versions are as shown in

Table 7.4. Table 7.4 UPI-41,42 Family UPI device

ROM bytes

EPROM bytes

RAM bytes

8042 AH

2K

S

256

2K

256

8742 AH 8041 AH 8741 AH

1K

128 1K

128

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Other important features are: 8-bit timers/counters, 18 programmable I/O lines, one 8-bit status and two data registers for asynchronous slave-to-master interface, expandable I/O, sync. mode available, over 90 instructions, intelligent programming algorithm, available in 40-lead cardio 40-lead plastic and 44-lead plastic leaded chip carrier packages, etc.

ARITHMETIC PROCESSORS General purpose microprocessors such as 8086. 8088,80286, 80386 etc. arc not optimized to perform complex numerical calculations, CRT graphics manipulations or word processing. For these purposes specialized coprocessors have been developed. For example, the 8087 is a numeric data coprocessor for numerical calculation, and 82786 is a graphic coprocessor. These coprocessors operate in parallel with CPUs.

There are two ways to interface an arithmetic processor to a CPU. In one approach it is treated as a peripheral device. Such units are called peripheral processor. The CPU sends data and instructions for processing to such an unit and receives results from it. Examples of peripheral arithmetic processors are AMD 9511/12, Intel 8231A, etc. In another approach the arithmetic processor is connected as an extension of the CPU. The instructions and registers of arithmetic processor are extensions to those of the CPU. The instruction set of the CPU includes a special subset of opcodes reserved for arithmetic processor. Arithmetic processor of this type is called coprocessor. Unlike a peripheral processor, a coprocessor is designed for a particular CPU family, whereas a peripheral processor can be used with any host CPU. Each CPU is designed with a coprocessor interface that contains special control circuitry to link CPU with the coprocessor, and special instruction for coprocessor. Examples of numeric data coprocessors are Intel 8087.80287,80387 etc.

Intel 8087 It is a high performance numeric data coprocessor. Its other versions are 8087-1 and 8087-2. It uses HMOSIII technology and is packed in 40-pin package. Clock rates for 8087 are 5 MHz. for 8087-2. 8 MHz and for 8087^1, 10 MHz. It has been designed to work with 8086. 8088, 80186 and 80188 microprocessors. It has 68 numeric processing instructions which are

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added to 8086/8088 instructions set. The 8087 includes the standard 8086/8088 instruction set for general data manipulation and program control. Its 68 numeric instructions are for extended precision integer, floating-point, trigonometric, logarithmic and exponential functions. It includes instructions for arithmetic operations. It contains eight 80-bit registers which are added to the register set of the CPU. It can handle 16, 32 and 64-bit integers; 64. 80-bit floating-point and 18-digit BCD operands. It also provides the capability to control round off, underflow, and overflow errors in each calculation. The trigonometric, logarithmic and exponential functions are built into the coprocessor hardware. At hardware level it is treated as the extension to the CPU. providing register, data types, control and instruction capabilities. As a coprocessor to 8086 or 8088 the 8087 is connected in parallel with the CPU. At the programmer's level the 8087 and the CPU are treated as a single unified processor. The 8087 executes instructions as a coprocessor to a maximum mode CPU.

Intel 80287,80C287A The 80287 is a HMOS numeric processor extension for 80286 microprocessor. It has 80-bit internal architecture. Its various versions are 80287-3, 80287-6, 80287-8 and 80287-10 to operate at different clock rates. It has over 50 instructions which are added to the instruction set of 80286. It is object code compatible with 8087. It executes instructions in parallel with an 80286. It directly extends 80286 instruction set to trigonometric, logarithmic, exponential and arithmetic instructions for all data types. The data types include 32, 64 and 80-bit floating-point: 32. 64-bit integers and 18-digil BCD operands. It can perform full-range transcendental operations for sine. cosine, tangent, arctangent and logarithm. It contains 8 x 80-bit individually addressable numeric register stack. Protected mode operation completely conforms to the 80286 memory management and protection. It is packed in 40-pin cerdip package. The 80C287A is a CHMOS III math coprocessor designed for higher speed and low power consumption.

Intel 80387 DX It is a high performance 80-bit CHMOS IV numeric processor extension for 80386 DX microprocessor. It has 80-bit internal architecture. Its performance is 5 to 9 limes more than

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that of 8087 and 80287. It handles 32. 64 and 80-bit floating-point; 32 and 64-bit integers and 18-bit BCD operands. It directly extends 80386 DX CPU instruction set to include trigonometric, logarithmic. exponential and arithmetic instructions for all data types. It is upward object-code compatible, with 8087 and 80287. It has built-in exception handling. It effectively extends the registers and instruction set of 80386 microprocessor. It adds over 70 mnemonics to 80386 DX instruction set. It is packed in 68-pin PGA package. Programmers may use the registers of 80387 DX in addition to the registers of 80386 DX microprocessor.

Intel 80387 SX It is a high performance 80-bit numeric processor extension for 80386SX microprocessor. Its internal architecture is of 80-bits. Its performance is ?-3 times more than that of 8087 and 80287. It is compatible with 80387 DX. It is upward object-code compatible with 8087 and 80287. It can handle 32, 64 and 80-bit floating-point; 32, 64-L.i integer and 18-digit BCD operands. It directly extends 80386SX CPU instructions set to trigonometric, logarithmic, exponential and arithmetic instructions for all data types. It adds over seventy mnemonics to the instruction set of 8U386SX microprocessor. It has built-in exception handling. It is available in 68-pin PLCC package. Programmers may use the registers of 80387SX in addition to those of 80386SX microprocessor.

Motorola MC68881 It is a floating-point coprocessor of Motorola. It contains eight 80-bit general purpose registers, and 3 status and control registers. It contains a number in extended-precision format with sign, 15-bit exponent, and 64-bit mantissa.

MOTHERBOARD The motherboard is the main circuit board inside the computer, and it normally forms the ''floor" of the system unit. Plugged into the motherboard in some way are all the electrical components of t he computer. Of foremost importance is the central processing unit (CPU) or microprocessor. The CPU chip is considered the brains of the computer; it controls the flow and the processing of data. The math coprocessor is another type of chip that might be found on

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the motherboard. The math coprocessor helps the CPU perform complex mathematical calculations. Newer CPUs contain an internal math coprocessor. Memory chips are an essential part of the computer, and they too are found on the motherboard. .Memory (RAM) chips are used to temporarily store data while the computer is processing it.

Bus Architecture 10.1 INTRODUCTION Important types of bus Architecture used in a computer system are: (i)

ISA Bus

(ii)

EISA Bus

(iii)

MCABus

(iv)

Local Bus: VL Bus, PCI Bus

ISA BUS ISA is the abbreviation of industry standard architecture. It is pronounced as e-sah. 11 has 24 address lines and 16 data lines. It is used in 386 and 486 single user system. It doesn't lake full advantage of the 32-bit address bus and 32-bit data bus of a 32-bit microprocessor. This reduces the data transfer rate of the system. This problem can be solved to some extent using a 32-bit bus between the CPU and memory, and employing a catche on the motherboard. This technique allows the CPU to access memory at the full speed of a 32-bit microprocessor. In such a system ISA bus(a 16-bit expansion bus) is used to transfer data from peripherals such as disk controller board, CRT controller board, printer, etc. In a single user system the limitations of an ISA bus do not have appreciable effect on the performance of the system. The advantages of an ISA bus are its low cost and availability of many peripheral boards for it. Fig. 10.1 shows a typical example of an ISA bus.

EISA BUS For a multiuser/multitasking system ISA bus is not suitable because of its low data transfer rate. Also, there is no mechanism for bus arbitration. EISA and MCA bus architectures

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are suitable for multiuser system. EISA is abbreviation for extended industry standard architecture. It uses 32-bit address bus and 32-bit data bus to fulfil the needs of a 32-bit microprocessor. Data transfer rate of EISA is twice that of ISA.

In a multiprocessor system the processor which takes over the control of buses is called a bus master. The controller which lakes over the control of

Buses for DMA data transfer is called a DMA slave. The EISA bus system can support up to 6 bus masters and 8 DMA slaves.

EISA bus system is 100% compatible with ISA 8-bit expansion boards and software, EISA connector is superset of the ISA connector to main train full compatibility with ISA expansion cards. ELSA connector contains two bottom layer contacts are the contacts for additional EISA signals. The connectors of the EISA bur are of the same physical size as that of an ISA bur connector so that either ISA of EISA cards can be inserted in the EISA connector slot.

82350 EISA Chip Set The EISA chip set includes following three Ics: 82352 EISA Bus Buffers (EBB) (optional)

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82357 Integrated System Peripheral (ISP) 82358 EISA Bus Controlled (EBC) The EISA chip set can support 386 and 486 CPU, 82385 cache controller and optional numeric corprocessor. It is EISA/ISA compatible chip set. Fig 10.2 shows 486 based system with 82350 EISA chip set. TliC host CPU is the main system processor located on a separate bus called host bus. This uses EISA bus controller and other system board facilities to interlace to the EISA bus.

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82350DT EISA Chip Set The 82350DT EISA chip set contains 7 VLSI cliips to build a complete EISA system, ll is built upon the 82350 EISA chip set utilizing the 82358DT EBC and 82357 ISP and then adds VLSI components: 82359 DRAM controller, 82353 Advanced Data Path. and 82351 LIOE Local 10 Peripheral. Fig. 10.3 shows 486 based syslein with 82350DT chip set. The host bus connects the CPU and the memory subsystem. The peripheral bus(X-bus) is an 8-bit bus to support the motherboard 10 functions: keyboard, floppy and the LIOE(local I/O EISA support peripheral) which integrates the parallel ports: and supports external real lime clock and serial ports. The peripheral bus is a buffered version of the 8-bil ISA bus. The memory subsection operates independent of the CPU clock. This independence is accomplished through the use of 82359's integrated programmable delay line and the programmable stale tracker (PST) function. The integrated programmable delay line is used to tune precisely the DRAM cycle sequence to DRAM parameters. The PST resides on the CPU module. The 82359/82353 reside on the motherboard. They arc indifferent to the CPU/cache used. The PST converts processor cycles to a form acceptable to the 82359. This allows different CPU/ cache combinations to be connected to the same motherboard. Further, it translates CPU's clockdependant handshake to clock less memory interface handshake.

Lot-ill I/O EISA Support Peripheral (LlOE), Intel 82351 The 82351 supports or integrates all of the I/O peripheral functions for a typical EISA system board with a minimum of external logic. It integrates local I/O address decoder, EISA system configuration registers, two external serial I/O controller interfaces will four assignable interrupts generation, external EISA configuration RAM interface, parallel port interface, external floppy disk controller interface, external keyboard (8x42) controller interface including interrupt generation, and external real lime clock interface and EPROM or FLASH EPROM BIOS ROM interface. It is available in a 132-pin PQFP (Plastic Quad Flat Pack) package.

EISA Bus Buffer (EBB), Intel 82352 The 82352 is a bus buffer 1C for EISA bus system. Three 82352 chips are used in a 82350 EISA system. Only one 82352 chip is used in a 82350DT EISA system. It operates in three

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modes. In Mode 0 it performs data latch and swap functions. It allows swapping and assembly of data between the host and EISA/ISA buses on a byte by byte basis. In Mode 1 it provides a buffered path between the host data bus and DRAM with parity generation/check. The Mode 2 is reserved by Intel for future system. Mode 3 provides address latching function between the host and EISA/ISA buses. The 82352 is available in a 120-pin quad flat pack(QFP).

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Advanced Data Path, Intel 82353 The 82353 provides advanced data path in a 82350DT EISA bus system. Two 82353 chips are used in a 82350DT EISA bus system as shown in Fig. 10.3. Each 82353 is designed as a 16-bit slice. Two 82353 chips can provide parallel interface to 32,64 or 128- bit wide memory structures to a 32-bit host and system bus. The 82353 provides optimal 486 burst performance. Each memory cycle generated by the address controller chip causes 128 bits of memory data to be latched in two 82353 chips. Once data is latched, these 82353 chips mux the four dwords to the destination in zero wait state. The 82350DT EISA bus has 128-bit memory bus. A typical burst is 128-bit wide, and a bus with the same width allows to read the whole burst in one memory cycle. This provides a zero wait state burst at any frequency. The82353 is available in a 164-pin PQFP package.

Integrated System Peripheral (ISP), Intel 82357 The

82357

contains

DMA controllers, interrupt

controllers

and

programmable

16-bit

counter/timers. It provides high performance arbitration for CPU, EISA/ISA bus masters, DMA channels and refresh. It also provides logic for generation/control of nonmaskable interrupts. The DMA function is provided by inbuilt two 82C37A DMA controllers. These DMA controllers are connected in cascade mode to provide seven independent programmable channels. The timing control for 8-, 16- and 32-bit DMA data transfer is provided. The data transfer rate is 33MB/sec. There are two 82C59A interrupt controllers in 82357 chip, which provide 14 independent, programmable channels for level or edge-triggered interrupts. The 82357 contains five 82C54 compatible programmable 16-bit timers/counters. It is available in a 132pin PQFP(plastic quad flat-pack) package.

EISA Bus Controller, Intel 82358DT The 82358DT provides an interface between 386/486 CPU and EISA bus system. It provides EISA/ISA bus cycle compatibility with the host(CPU) bus. The 82358DT is a part of Intel 82350 and 82350DT chip sets. It translates host(CPU) and 82359(DRAM controller) cycles to EISA/ISA bus cycles. It supports 8-, 16-or 32-bit DMA cycles. It also supports host and EISA/ISA refresh cycles. It generates

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control signals for advanced data path(82353) and EISA bus buf-fer(82352). It is available in a 132-pin PQFP package. DRAM Controller, Intel 82359 The 82359 is a highly integrated advanced memory controller. It supports 386 and 486 microprocessors. Its operation is independent of speed and type of the CPU. It allows a system designer to implement a variety of CPU/cache combinations. It provides address control, refresh generation and critical DRAM timing generation. In conjunction with two advanced data path devices (82353), it acts as a highly integrated 32-bit dual ported memory controller. Its two ports(or address gateways) to main memory are: one exclusively for the host and one exclusively for EISA. This configuration of ports permits CPU activity to be isolated from EISA bus activity. It controls up to 256MB of motherboard DRAM. It supports 32-, 64- or 128-bit wide memory configurations. It is available in a 196-pin PQFP package.

Bus Master Interface controller, Intel 82355 The 82355 is used in an EISA add-in card(expansion board) as shown in Fig. 10.2. It supports 16- and 32-bit burst transfers at maximum data transfer rate of 33MB/sec. It also supports 32-bit nonburst and mismatched data size transfers. It automatically handles misaligned doubleword data transfer with no performance penalty. It has two independent data transfer channels with 24-byte FIFOs. Expansion board timing and EISA timing operate asynchronously. The 82355 supports 32-bit EISA addressability (4GB). It integrates three interfaces: EISA. local CPU, and transfer buffer. It supports automatic handling of complete EISA bus master protocol. This includes EISA arbitration/preemption, cycle timing and execution, byte alignment, etc. Further, the 82355 supports local data transfer protocol similar to traditional DMA. It is available in a 132-pin JEDEC PQFP package.

MCA BUS MCA is abbreviation for MicroChannel Architecture. It has been developed by IBM. It contains the same types of signals and performs the same functions as an EISA bus but the MCA and EISA bus architectures are completely incompatible.

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LOCAL BUS The ISA. EISA and MCA bus are not able to fulfil the data transfer rate required by 32-bit and 64bit powerful computers available today. In a local bus system peripherals are connected to a local bus as shown in Fig. 10.4. A local bus system with its 32-bit data path and 33 MHz clock speed can transfer data at higher rate compared to ISA bus, which has 16-bit data path and 8 MHz clock speed. Its data transfer rate (130MB per second) is about 6 times faster than that of an ISA bus(20MB per second). There are two local bus standards: Video Electronic Standards Association’s (VESA's) VL and Peripheral Component Interconnect(PCI) as discusses below.

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VL Bus It is VESA's local bus. It appeared at the end of 1992. It is particularly suitable for graphics applications but it can also be used to improve the speed of other compatible peripherals. It is designed to work with the RISC R4000 and Intel 80x86 family of microprocessors. The VL architecture incorporates a bus controller to arbitrate between bus masters and the CPU. The VL bus allows up to three bus masters. Although the VL bus currently uses a 64-bit expansion capability and the physical slot, specification allows for the larger socket size for the future. The VL bus has not been designed to replace a conventional expansion bus, rather it is to be used as an addition to a conventional bus.

The VL bus includes only one hardware interrupt control line(corresponding to IRQS) which is used to hook into an ISA, EISA or MCA bus. This permits VL bus peripherals to take the benefit of the resources of (lie other expansion bus(in-terrupts. DMA control etc.) including level-triggered interrupts when these are supported by the host bus.

VL Bus 20 Version This version was introduced in 1993, with the release of Intel's 64-bit Pentium microprocessor. Its specifications provide a 64-bit interface. It is compatible with VL bus.

PCI Bus PCI has been developed by Intel. It is a 32-bit local bus which extends the processor's own local bus, and can be expanded up to 64-bit when need arises. It offers higher performance, automatic configuration of peripheral cards and superior compatibility. It is a costly system. The PCI bus system is able to support ten devices because PCI devices do not electrically load down the CPU bus whereas VL bus can support only up to three local bus peripherals. Logical, mechanical and electrical specifications of PCI bus have been given very clearly whereas specifications of VL bus are of loose nature. The PCI bus system can transfer data at a rate of 130MB per second at 33MHz.

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PCI bus is a high performance connection between the motherboard components and expansion boards of a system. There is a bridge-chip between the processor and the PCI bus, which connects the PCI bus to the processor's local bus. This allows to connect PCI peripherals directly to the PCI bus. Once a host bridge chip is included in the system, the processor can access to all available PCI peripherals. This makes the PCI bus standard processor independent. When a new processor is to be used, only the bridge-chip needs to be replaced; the rest of the system remains unchanged. The PCI bus employs a 124-pin, microchannel style connector(188 pins for a 64-bit system). PCI specifications are for two types of connection: 5V system and 3.3V low power system. PCI design have ability to support future generations of peripherals. Self-assessment question

7. Ram means _____________ 8. What is a mother board? 9. Bus means______________ Answer: 7. Read only memory 8. It in a main board, on which CPU and other parts are placed. 9. It is a common path way on which data can travel within a computer.

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UNIT - II COMPUTER PERIPHERALS INPUT DEVICES Data and instructions are entered into a computer through input devices. An input device converts input data and instructions into suitable binary form which can be accepted by the computer. The commonly used input device is a keyboard. A number of input devices have also been developed which do not require typing for inputting information. Examples arc: mouse, light pen, graphic tablet, joy stick, track ball, touch screen etc. Each of these devices permits the user to select something on CRT screen by pointing to it. Therefore, these devices are called pointing devices. Voice input systems have also been developed. A microphone is used as an input device.

Keyboards Programs and data are entered into a computer through a keyboard which is attached to a microcomputer or the terminal of a mini or large computer. A keyboard is similar to the keyboard of a typewriter. It contains alphabets, digits, special characters and some control keys. When a key is pressed an electronic signal is produced which is detected by an electronic circuit called keyboard encoder.

Mouse (Puck) A mouse is also a pointing device. It is held in one hand and moved across a flat surface. Its movement and the direction of the movement is detected by two rotating wheels on the underside of the mouse. The wheels have their axes at right angles. Each wheel is connected to a shaft encoder which emits electrical pulses for every incremental movement of the wheel. The pulses transmitted by the mouse determine the distance moved.

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When a user moves the mouse across a flat surface, the cursor on the CRT screen also moves in the direction of the mouse's movement. By moving the mouse the user can point to menu on the screen. By pressing the button on th ' mouse, the user communicates his choice to the computer.

Light Pen A light pen is a pointing device. It is used to select a displayed menu option on the CRT. It is a photosensitive penlike device. It is capable of sensing a position on the CRT screen when its tip touches the screen. When its tip is moved over the screen surface, its photocell sensing element detects the light coming from the screen and the corresponding signals are sent to the processor.

Joystick A joystick is also a pointing device. It is used to move the cursor position on a CRT screen. Its function is similar to that of a mouse. A joystick is a stick which has spherical ball at its lower end The joystick can be moved right or left forward or backward. The electronic circuitry inside the joystick detects and measures the displacement of the joystick from its central position; the information is sent to the processor.

Push button Switches

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Self Assessment Questions

01. Keyboard is an _______________________________ 02. Mouse in an ______________________________________ device

device

03. What is joy stick? Answer 01. Input 02. Input 03. Joy stick is an input device, used to transfer the data into the computer. Trackballs Trackball is also a pointing device and contains a ball which can rotate in any direction. The user spins the ball in different directions to move the cursor on the CRT screen.

Scanners Scanners are a kind of input devices. They are capable of entering information directly into the computer. The main advantage of direct entry of information is that users do not have to key the information. This provides faster and more accurate data entry. Important types of scanners are optical scanners and magnetic-ink character readers.

Optical Scanners The optical scanners are capable of reading information recorded on paper, employing light source and light sensors. The information to be scanned is typewritten information, information coded as ink or pencil marks or information coded as bars. The following are the commonly used optical scanners:

Optical Mark Reader (OMR) Special marks such as square or bubble are prepared on examination answer sheets or questionnaires. The users fill in these squares or bubbles with soft pencil or ink to indicate their choice. These marks are detected by an optical mark reader and the corresponding signals are sent to the processor. If a mark is present, it reduces the amount of reflected light. If a mark is not present, the

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amount of reflected light is not reduced . This change in the amount of reflected light is used to detect the presence of a mark. This method is used where one out of a few number of alternatives is to be selected and marked. For example, market survey, population survey, objective type answer sheets etc. where choice is restricted to one out of a few choices.

Optical Character Readers (OCR). An optical character reader detects alphanumeric characters printed or typewritten on paper. It may be a handheld scanner or a page scanner to detect light reflected from a line or from a page of the text. The change in the reflected light is converted to binary data which is sent to the processor. The text which is to be scanned is illuminated by a low-frequency light source. The light is absorbed by the dark areas while the light is reflected from the lighted areas. The reflected light is received by photocells or CCDs (charged coupled devices) which provide binary data corresponding to dark and lighted areas. An OCR can scan several thousands primed or typewritten characters per second. Optical character readers are used in large-volume applications such as computer-oriented bills prepared by public utilities.

Optical Bar-Code Readers This method uses a number of bars (lines) of varying thickness and spacing between them to indicate the desired information.

An optical-bar reader can read such bars and convert them into electrical pulses to be processed by a computer.

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Self-Assessment Questions

04. OMR means____________________________________ 05. OCR means ____________________________________ 06. What is bar code reader? Answer 04. Optical mark reader. 05. Optical character reader 06. Is a reader and is used to identify the bars.

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Magnetic-Ink Character Reader (MICR) MICR is widely used by banks to process large volumes of cheques and deposit forms written every day. A special ink called magnetic ink (i.e. an ink which contains iron oxide particles) is used to write characters on the cheques and deposit forms which are to be processed by an MICR. MICR is Capable of reading characters on a paper written with magnetic ink.

Upto 2600 cheques are processed per minute, by an MICR.

Voice Input Systems Data entry into a computer manually using keyboard is a time-consuming and laborious task. It will become very easy if we can talk to a computer.

In a voice input system the speech is converted into electrical signals employing a microphone.

Game Controllers You may not think of a game controller as an input device, but it is. Personal computers are widely used as gaming platforms, challenging dedicated video game units like the Sony PlayStation and others. Because PCs offer higher graphics resolution than standard televisions, many gamers believe a well-equipped PC provides a better game-playing experience. If your computer is connected to the Internet, you can play games with people around the world.

A game controller can be considered an input device because a computer game is a program, much like a word processor. A game accepts input from the user, processes data, and produces output in the form of graphics and sound. As computer games become more detailed and elaborate, more specialized game controllers are being developed to; take advantage of their features.

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Game controllers generally fall into two broad categories: game pads and joysticks (see Figure 2B.6). Joysticks have been around for a long time and can be used with applications other than games. (Some joystick users actually prefer using a joystick rather than a mouse with some business applications.) Joysticks enable the user to "fly" or "drive" through a game, directing a vehicle or character. They are popular in racing and flying games. A variant of the joystick is the racing game controller, which includes an actual steering wheel; some racing game controllers even include foot pedals and gearshifts.

Touch screen Touch screens accept input by allowing user to place a fingertip directly on the computer screen, usually to make a selection from a menu of choices. Most touch-screen computers use sensors on the screen's surface to detect the touch of a finger, but other touch screen technologies are in use, as well.

Touch screens work well in environments where dirt or weather would render keyboards and pointing devices useless, and where a simple, intuitive interface is important. They are well-suited for simple applications, such as automated teller machines or public information kiosks. Touch screens have become common in fast-food restaurants, department stores, drugstores, and supermarkets, where they are used for all kinds of purposes, from creating personalized greeting cards to selling lottery tickets.

Digital Cameras Digital cameras work much like PC video cameras, except that digital cameras are

v

portable,

handheld devices that capture still images. Whereas normal film cameras capture images on a specially coated film, digital cameras capture images electronically. The digital camera digitizes the image, compresses it, and stores it on a special memory card. The user can then copy the information to a PC, where the image can be edited, copied, printed, embedded in a document, or transmitted to another user.

Most digital cameras can store dozens of high-resolution images at a time, and most cameras accept additional memory that increases their capacity even further. Moving digital images from a digital camera to a computer is a simple process that uses standard cables, disks, or even infrared networking

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capabilities. A wide range of digital cameras are available, from inexpensive home-use models

to

professional versions costing several thousand dollars.

Web Camera and Its Uses The video cameras used with computers digitize images by breaking them into individual pixel. (A pixel is one or more dots that express a portion of an image). Each pixel’s color and other characteristics are stored as digital code. This code is then compressed (video images can be very large) so that it can be stored on disk or transmitted over a network.

A popular and inexpensive type of PC video – camera called a webcam – can sit on top of a PC monitor or be placed on a stand, so the user can “Capture” images of himself or herself while working at the computer. This arrangement is handy for videoconferencing, where multiple users see and talk to one another in real time over network or internet connection.

MEMORY DERIVES Magnetic Memory The magnetic memories are permanent memory. They are not volatile. The following are the types of magnetic memory: (iv)

Floppy disks

(v)

Hard disks

(vi)

Magnetic tapes

Floppy Disks Floppy disks are commonly used as secondary and backup memory in personal computers. They are also called diskettes. These disks are very thin and flexible and hence, they are called floppy. These are made of Mylar with a coating of magnetic material (iron oxide) on it. They are small, convenient and inexpensive. They are removable disks. A floppy disk is inserted into the computer when needed. If the same disk is to be used again and again, it can be kept inserted in the system. It is kept in a square

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protective cover made of thin plastic. The disk rotates freely in the protective cover (jacket). The most popular sizes of floppy disks are: 5.25 inches square and 3.5 inches square.

Self-Assessment Questions

7. Scanner is an ____________ device 8. Two types of memories are __________________ 9. What is touch screen? Answer 7. Input 8. Primary, Secondary 9. Screen which senses by touching the finger.

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UNIT – III PRINTER Printers are commonly used output devices. They provide information in a permanent readable form. They produce printed output of results, programs and data. Printers which are used with computers arc classified as follows: (i)

Character printers

(ii)

Line printers

(iii)

Page printers A character printer prints one character of the text at a time. A line printer prints one line of the

text at a time. A page printer prints one page of the text at a time.

The printers have been classified above as to how they print. There is one more classification which depends on the technology used in their manufacture. According to this consideration the printers are classified into the following two broad categories: (i)

Impact printers

(ii)

Nonimpact printers Impact printers use electromechanical mechanism that causes hammers or pins to strike against

a ribbon and paper to prim (he text. Non-impact printers do not use electromechanical printing head to strike against ribbon and paper. They use thermal, chemical, electrostatic, laser beam or inkjet technology for printing the text. Usually a nonimpact type printer is faster than an impact type printer. The disadvantage of nonimpact type printers is that they produce single copy of the text whereas impact printers produce multiple copies of the text.

Line Printers A line printer prints one line of the text at a time. Its printing speed lies in the range of 300-3000 lines per minute. It is used for large-volume printing job. It may be used with mini and large computers. The impact type line printers are of the following types:

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Drum printer

(ii)

Chain printer

(iii)

Band printer

52

Drum Printers A drum printer uses a rapidly rotating drum (cylinder) which contains a complete raised characters set in each band around the cylinder. Each character position along the text line contains a band of raised character set. There is a magnetically driven hammer in each character position of the line. The printer receives all characters to be printed in one line of the text from the processor. The hammers hit the paper and ribbon against the desired character on the drum when it comes in the printing position. Its noise level is high. Its speed varies from 200 to 2000 lines per minute. Chain printers use a rapidly rotating chain which is called print chain. The prim chain contains characters. Each link of the chain is character font. Magnetically driven hammers are there in each print position. The printers receive all the characters to be printed in one line from the processor. Primers print one line at a time. A chain may contain more than one character set. for example 4 sets, around it. When the desired character comes in the print position the hammer strikes the ribbon and paper against the character. The noise level of the printer is high. Its speed lies in the range of 400-7400 lines/min. Band Printers Band printers are just like chain printers. They contain fast rotating scalloped steel print band in place of a chain. The print band contains raised character set. Hammers strike the ribbon and the paper against the character to print the character. Some printers can print upto 3000 lines/mill. Their noise level is high.

Page Printers Page printers are nonimpact type printers. They print one page at a lime. These printers use laser or other light printers use laser or other light source to produce an image on a photosensitive drum. The computer controls the laser beam to turn it on and off when it is sent back and forth across the drum. An image is produced on the raster scan principle as it is produced on a CRT. The laser-exposed areas

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attract toner (an ink powder). Thereafter the drum transfer the toner to the paper. The paper then moves to a fusing station where the toner is permanently fused op (he paper with heat or pressure. After this the drum is discharged and cleaned. Now the drum is ready for processing the next page. The laser printers are quiet and they produce high-quality output. These printers are expensive and require a lot of maintenance. Low-speed laser printers producing 10 pages or more per minute are used with microcomputer. High-speed laser printers producing upto 300 pages per minute are manufactured for mini and large computers.

PLOTTERS Plotters are output devices. They are used to produce precise and good quality graphics and drawings under computer's control. They use ink pen or ink-jet to f draw graphics or drawings. Either single colour or multicolour pens can be employed. The pens are driven by motor. Drawings can be prepared on paper.

Drum Plotters A drum plotter contains a long cylinder and a pen carriage. The paper is placed over the drum (i.e. cylinder). The drum rotates back and forth to give up and down movement. The pen is mounted horizontally on the carriage. The pen moves horizontally along with the carriage left to right or right to left on the paper to produce drawings. Under the computer control both the drum and the pen move to produce the desired drawings. Several pens with ink of different colours can be mounted on the carriage for multicolour drawings.

Flat-Bed Plotters Such plotters use horizontal Hat surface on which paper, vellum, mylar or any other medium can be fixed. The pen moves along both axes:

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Self Assessment Question

01. Printer is an ____________________________ device 02. Plotter is an __________________________ device 03. What is impact type printer?

Answers: 01. Output 02. Output 03. Which strikes the ribbon and produces the images

Multimedia Devices Multimedia is the combination of text, graphics, sound, video, and animation in a single presentation. Because of its flexibility, multimedia is often used to provide training and instruction to employees in large companies, to teach and introduce new topics of learning in the educational fields, and to provide advertising and information in a shopping mall kiosk (information booth). Multimedia incorporates such computer hardware as CD-ROMs and sound boards to produce innovative and exciting visual presentations.

Multimedia presentations are currently very popular in library and educational settings. A user can open an encyclopedia file on a CD-ROM disc to the word "elephant," and not only does the file contain text describing the environment and habits of the elephant, but it also shows a video of an elephant on the plains of Africa, complete with sound. Such presentations are very effective in gaining attention, allowing users to interact with the computer, and making complex information much easier to understand. To create and view multimedia presentations, a computer must have additional peripherals (hardware) to support the variety of media used. Such a PC usually carries the MPC symbol (for multimedia PC),

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meaning that it meets the standards established by the Multimedia PC Marketing Council. An MPC compatible CD-ROM drive is of foremost importance. CD-ROMs (Compact Disc Read-Only Memory), are a storage disk used to save vast amounts of data, including sound, animation, video, and graphics. CDROMs are the primary source for storing multimedia files. In addition, an MPC must have at least an 80486SX CPU, 8 megabytes of RAM, a clock speed of 25 Mhz, a hard disk with 160 megabytes of free space, a VGA monitor, an MPC compatible 16-bit sound card, speakers, and Microsoft Windows. SOUND CARD The most complicated part of a computer's sound system is the sound card. A computer's sound card is a circuit board that converts sound from analog to digital form, and vice versa, for recording or playback. A sound card actually has both input and output functions. If you want to use your computer's microphone to record your voice, for instance, you connect the microphone to the sound card's input jack. Other audio input devices connect to the sound card as well, such as the computer's CD-ROM or DVD drive. You may be able to attach other kinds of audio devices to your sound card, such as tape players, record players, and others. The sound card accepts sound input (from a microphone or other device) in the form of analog sound waves. You can think of analog signals as fluctuations in the intensity of an electrical current. The sound card measures those signals and converts them into a digital format, which the computer can use. Audio Output Devices To play back audio, the sound card reverses the process. That is, it translates digital sounds into the electric current that is sent to the speakers, which are connected to the card's output jacks. Optical Devices Information is written to or read from an optical disk using laser beam. An optical disk has very high storing capacity, for example, a 5.25 inch optical disk stores 550 MB. Only one surface of an optical disk is used to store data. An optical disk is relatively inexpensive, and has a long life of at least 20 years. Its drives are inherently simple and inexpensive. As the read/write head does not touch the disk surface, there is no disk wear and no problem of head crash. Floppy and Floppy Drive Device Floppy drive includes a motor a includes a motor that rotates the disk on a spindle and read/write heads that can move to any spot on the disk’s surface as the disk spins. The heads can skip from one

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spot to another on the disk's surface to find any piece of data without having to scan through all of the data in between.

Self Assessment Question

04. Types of printers are __________________________ 05. Multimedia technique are _______________________ 06. What is audio – output device?

Answers: 04. Character, line, page 05. 3D Graphics, Animation, Morphing 06. Which produces the output in the form of Voice.

Diskettes spin at about 300 revolutions per minute. Therefore, the longest it can take to position a point on the diskette under the read/write heads is the amount of time required for one revolution-about 0.2 second. The farthest the heads have to move is from the center of the diskette to the outside edge (or vice versa). The heads can move from the center to the outside edge in even less time-about 0.17 second. Because both operations (rotating the diskette and moving the heads from the center to the outside edge) take place simultaneously, the maximum time to position the heads over a given location on the diskette-known as the maximum access time-remains the greater of the two times, or 0.2 second (see Figure 5A.10).

The maximum access time for diskettes can be longer, however, because diskettes do not spin when they are not being used. It can take about 0.5 Second to rotate the disk from a dead stop.

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A 3.5-inch diskette, as shown in Figure 5A.11, is encased in a hard plastic shell with a sliding shutter. When the disk is inserted into the drive, the shutter is slid back to expose the disk's surface to the read/write head.

The sectors near the middle of the CD wrap farther around the disk near than those the edge. For the drive to read each sector in the same amount of time, it must spin the disc faster when reading sectors near the middle and slower when reading sectors near the edge. Changing the speed of rotation takes time-enough to seriously impair the overall performance of the CD-ROM drive.

The first CD-ROM drives could read data at 150 KBps (kilobytes per second) and were known as single-speed drives. Today, a CD-ROM drive's speed is expressed as a multiple of the original drive's speed-2x, 4x, 8x, and so on. A 2x drive reads data at a rate of 300 KBps (2 X 150). At the time this book was published, the fastest available CD-ROM drive was listed at a speed of 75x; it could read data at a rate of 11,250 KBps (or slightly more than 11 MBps).

The 360K 5 1 /4 Inch Drive The5 1/4 Inch low-density drive is designed to create a standard-format disk with 360K capacity.

Although I persistently call these low-density drives, the industry term is “double-density” I use “lowdensity” because I find the term “double-density" to be somewhat misleading, especially when I am trying to define these drives In juxtaposition to the high-density drives.

The term double-density arose from the use of the term single-density to indicate a type of drive that used frequency modulation (FM) encoding to store approximately 90 kilobytes on a disk. This type of obsolete drive never was used in any IBM-compatible systems, but was used in some older systems such as the original Osbome-1 portable computer. When drive manufactures changed the drives to use Modified Frequency Modulation MFM) encoding, they began using the term ''double-density" to Indicate it, as well as the (approximately doubled) Increase in recording capacity realized from this encoding method. All modern floppy disk drives use MFM encoding, including all types listed in this section. Encoding

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methods such as PM, MFM and RLI, variants are discussed in Chapter 14, "Hard Disk Drives and Controllers.

The 360K 5 l/4-lnch drive normally records 40 cylinders of two trade each, with each cylinder numbered starting with 0 closest to the outside diameter of the floppy disk, Head position (or side) 0 is recorded on the underside of the floppy disk and Head 1 records on the top of the disk surface; This drive normally divides each track into nine sectors, but it can optionally format only eight sectors per track to create a floppy disk compatible with DOS versions 1.1 or earlier. This type of format rarely (If ever) is used today.

The 360K 51/4-inch drives as supplied in the first IBM systems all were full-height units, which means that they were 3.25 inches tall. Full-height drives are obsolete now and have not been manufactured since 1986. Later units used by IBM and most compatible vendors have been the halfheight units, which are only 1.6 inches tall. You can install two half-height drives in place of a single fullheight manufacturers, are similar except for some cosmetic difference.

The 360K 5 1/4-inch drives spin at 300 RPM, which: equals exactly five revolutions per second, or 200 milliseconds per revolution. All standard floppy controllers support a 1:1 interleave, in which each sector on a specific track is numbered (and read) consecutively. To read and write to a disk at full speed, a controller sends data at a rate of 250,000 bits per second. Because all low-density controllers can support this data rate, virtually any controller supports this type of drive, depending on ROM BIOS code that supports these drives.

All standard IBM-compatible systems include ROM BIOS support for these drives; these-fore, you usually do not need special software or driver programs to use them. This statement might exclude some aftermarket (non-IBM) 360K drives for PS/2 systems that might require some type of driver in order to work. The IBM-offered units use the built-in ROM support to enable these drives to work. The only

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requirement usually is to run the setup program for the machine to enable it to properly recognize these drives.

The 1.2M 5 1/4-Inch Drive The I.2M high-density floppy drive first appeared n the IBM AT system introduced in August 1984. The drive required the use of a new type of disk to achieve the I.2M format capacity, but it still could read and write (although not always reliably) the lower-density 360K disks.

The I.2M 5 1/4-inch drive normally recorded 80 cylinders of two tracks each, starting with cylinder 0, at the outside of the disk. This situation differs from the low-density 5 1/4-inch drive in its capability to record, twice as many cylinders in approximately the same space on the disk. This capability alone suggests time the recording capacity for a disk would double, but that is not all. Each track normally is recorded with 15 sectors of 512 bytes each, increasing the storage capacity even more. In fact, these drives store nearly four times the data of the 360K disks. The density increase for each track required the use of special disks initially were expensive and difficult to obtain, many users attempted incorrectly to use the low-density disks in the 1.2M 5.1/4 inch drives and format them to the higher 1.2M-density format, which results in data loss and unnecessary data-recovery operations.

A compatibility problem with the 360K drives stems from the 1.2M drive’s capability to write twice as many cylinders in the same space as the 360K drives. The 1.2M drives position their heads over the same 40 cylinder positions used by the 360K drives through double stepping, a procedure in which the heads are moved every two cylinders to arrive at the correct-positions for reading and writing the 40 cylinders on the 360K disks. The problem is that because the 1.2M drive normally has to writ 80 cylinders in the same space in which the 360K drive writes 40 the heads of the 1.2M units had to be made dimensionally smaller. These narrow heads can have problems overwriting tracks produced by a 360K drive that has a wider head because the narrower heads on the I.2M drive cannot “cover� the entire track area written by the 360K drive. This problem and possible solutions to it are discussed rater in this chapter.

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The 1.2M 5 1/4 –inch drives spin at 360 RPM, or six revolutions per second, or 166.67 milliseconds per revolution. The drives spin at this rate no matter what type of disk is inserted-either lowor high-density. To send or receive 15 sectors (plus required over-head) six times per second, a controller must use a data-transmission rate of 500,000 bits per second (500 kilohertz, or kHz). All standard highand low-density controllers support this data rate and therefore, these drives. This support of course depends also on proper ROM BIOS support of the controller in this mode of operation. When a standard 360K disk is running in a high-density drive, it also is spinning at 360 RPM; a data rate of 300,000 bits per second (300 kHz) therefore is required in order to work properly. All standard AT-style low-and highdensity controllers support the 250kHz, 300 kHz and 500 kHz data rates. The 300 kHz rate is used only for high-density 5 1/4-inch drives reading or writing to low-density 5 1/4 inch drives reading or writing to low-density 5 1/4 inch disks.

Virtually all standard AT-style systems have a ROM BIOS that supports the controller’s operation of the 1,2M drive/including! the 300 kHz data rate.

The 720k3 1/2 Inch Drive The 720K, 3 1/2 –inch, double-density drives first appeared in an IBM system with the IBM convertible laptop system introduced in 1986. In fact, all IBM stystems introduced since that time have 3 1/2 drives as the standard supplied drives. This type of drive also is offered by IBM as an internal or external drive for the AT or XT systems. Note that outside the IBM-compatible word, other computersystem vendors (Apple, Hewlett Packard and so on) offered 3 1/2-inch drives for their systems well before the IBM-compatible world "caught on."

The 720K, 3 1/2-inch, double-density drive normally records 80 cylinders of two tracks each, with nine sectors per track, resulting in the formatted capacity of 720 kilobytes. It is interesting to note that many disk manufacturers label these disks as l megabyte disks, which is true. The difference between the actual 1 megabyte of capacity and the usable 720K after formatting is that some space on each track is

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occupied by the header and trailer of each sector, the Inter-sector gaps, and the index gap at the start of each track before the first sector. These spaces are not usable for data storage and account for the differences between the unformatted and formatted capacities. Most manufacturers report the unformatted capacities because they do not know on which type of system you will format the disk. Apple Macintosh systems, for example, .can store 800K of data on the same disk because of a different formatting technique. Note also that the 720K of usable space does not account for the disk areas D0S reserves for managing the disk (boot sectors, FATs, directories and so on) and that because of these areas, only 713K remains for file data storage.

IBM-compatible systems have used 720K, 3 1/2-inch, double-density drives primarily in XT-class systems because the drives operate from any low-density controller. The dives spin at 300 RPM and therefore require only a 250 kHz data rate from the controller to operate property. This data rate is the same as for the 360K disk drives, which means that any controller that supports 360K drive also supports the 720K drives.

The only issue to consider in installing a 720K, 3 l/2-lnch drive is whether the ROM BIOS offers the necessary support. An IBM system with a ROM BIOS date of 06/10/85 or later has built-in support for 720K drives and requires no driver in order to use them. If your system has an earlier ROM BIOS date, the DRIVER.SYS program from .DOS 3.2 or higher-as well as the DRIVEARM config.sys command in some OEM DOS versions-is all you need to provide the necessary software support to operate these drives. Of course; a ROM BIOS upgrade to a later version negates the need for "funny" driver software and is usually the preferred option when you add one of these drives to an older system,

The 1.44m 3 1/2 Inch Drive The 3 1/2-inch, 1.44M,high-density drives first appeared from IBM in the PS/2 product line introduced in 1987. Although IBM has not officially offered this type of drive for any of its older systems, most compatible vendors, started, offering the drives as options in systems immediately after IBM introduced the PS/2 system.

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The drives record 80 cylinders consisting of two tracks each with 18 sectors per track, resulting In the formatted capacity of 1.44 megabytes. Most disk manufacturers label these disks as2-megabyte disks and the difference between this unformatted capacity and the formatted usable result is lost during the format. Note that the 1.440K of total formatted capacity does not account for the areas DOS reserves for file management, leaving only 1423.5K of actual file-storage area.

These drives spin at 300 RPM and in fact must spin at that speed to operate properly with your existing high-and low-density controllers. To utilize the 500 kHz data rate, the maximum from most standard high-and low-density floppy controllers, these drives could spin at only 300 RPM if the drives spun at the faster 360.RPM ate of the 5 1/4-ineh drives, they would have to reduce the total number of sectors per track to 15 or else the controller could not keep up. In short, the 1.44M 3 1/2-inch drives store 1.2 times the data of the 5 1/4-Inch 1.2M drives and the' 1.2M drives spin exacey 1.2 times faster than the 1.44M drives. The data rates used by both high-density drives are identical and compatible with the same controllers. In fact, because these 31/2-Inch, high-density drives can run at the 500 kHz data rate, a controller that can support a 1.2M 51/4-inch drive can support the 1.44M drives also. If you are using a low-density disk in the 3 1/2-inch high-density drive, the data rate is reduced to 250 kHz, and the disk capacity is 720K. The primary issue, in. a particular system utilizing a 1.44M 3 1/2-inch drive is one of ROM BIOS support. An IBM system with a ROM BIOS date of 11/15/85 or later has built-in support for these drives and no external driver support program is needed. You might need a generic AT setup program because IBM's setup program doesn't offer the 1.44M drive as an option. Another problem relates to the controller and the way it signals the high-density drive to write to a low-density disk. The problem is discussed in detail in the following section. The 2.88M 3 1/2-inch Drive The-new 2.88M drive was developed by Toshiba Corporation in the 1980s and officially 1985, and then several vendors began selling the drives as upgrades for systems. IBM officially adopted these drives in the PS/2 systems in 1991 and virtually all PS/2s sold since then have these drives as standard

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equipment. Because a 2.88M drive can fully read and write 1.44M and 720K disks, the change was an easy one. DOS version 5.0 or higher is required to support the 2.88M drives.

To support the 2,88M drive, modifications to the disk controller circuitry were required because these drive spin at the same'300 RPM but have an astonishing 36 sectors per track. Because all floppy disks are formatted with consecutively numbered sectors (1:1 interleave), these 36'sectors, have to be read and written in the same time it takes a 1.44M drive to read and write 18 sectors. This requires that the controller support-a must-higher data transmission rate of 1 MHz (1 million bits per second). Most of the older floppy controllers either found on an adapter card or built into the motherboard supper only the maximum of 500 kHz data-rate used by the 1.44M drives. To upgrade to 2.88M drives would require that the controller be changed to one that supports the higher 1 MHz data rate.

An additional support issue-is the ROM BIOS. The BIOS must have support for the controller and the capability to-specify and accept the 2.88M drive as a CMOS setting. Newer motherboard BIOS sets from companies like Phoenix, AMI and Award have support for the new extra high density controllers.

In addition to the newer IBM PS/2 systems, most newer IBM clone and compatible systems now have built-in floppy controllers and ROM BIOS software that fully supports the 2.88M drives. Adding or upgrading to a 2.88M drive in these systems is as easy as plugging in the drive and running the CMOS setup program. For those systems who do not have this support built-in, this type of upgrade is much more difficult. Several companies offer new controllers and BIOS upgrades as well as the 2.88M drives specifically for up-grading order systems.

Although the 2.88M drives themselves are not much more expensive than the 1.44M drives they replace, the disk media is: currently still very expensive, Although you can purchase 1.44M discs for around (or under) one dollar each, the 2.88M disks can cost more than $5 per disk! As the drives become more generally available, the disk media prices should fall. The 1.44M and even 1.2M disk media also was very expensive when first introduced.

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Handling Recording Problem with 1.44M 3 1/2-inch Drives A serious problem awaits many users who use the 1.44M 31/2-inch drives; If the drive Is installed improperly, any write or format operations performed incorrectly on 720K disks can end up trashing data on low-density disks. The problem is caused by the controller's incapability to signal the high-density drive that a low-density recording will take place.

High-density disks require, a higher write-current or signal strength when they record than do the tow-density disks. A low-density drive can record at only the lower write-current, which is correct for the low-density disks; the high-density drive, however, needs to record at both high and low write-currents depending on which type of disk is inserted in the drive. lf a signal is not sent to the high-density drive telling it to lower or reduce the write-current level, the drive stays in its normal high write-current default mode, even when it records on a low-density disk.. The signal normally should be sent to the drive by the controller, but many controllers do not provide this signal properly for the 1.44M drives.

The Western Digital controller used by IBM enables i he reduced write-current (RWC) signal only if the controller also is sending data at the 300 kHz data rate, indicating the special case of a low-density disk in high-density drive. The RWC signal Is required to tell the high-density drive to lower the headwriting signal strength to be proper for the low-density disks. If the signal is not sent, the drive (defaults to the higher write-current, which should be used for only high-density disks. If he controller is transmitting the 250 kHz data rate, the controller knows that the drive must be a low-density drive and therefore no RWC signal Is necessary because the low-density drives can write only with reduced current.

This situation presented a serious problem for owner, of 1.44m drives using 720K disks because the drives Spin the disks at 300 RPM, and In writing to a low – density disk, use the 250 kHz data rate not the 300 kHz rate. This setup "fools" "thinking" that it is sending data to a low-density drive, which causes the controller to fall to send the requited. RWC signal. Without the RWC signal, the drive then records Improperly on the disk, possibly trashing any data being written or any data already present.

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Because virtually all compatibles use controller based on the design of the IBM AT floppy disk controller, most share the same problem as the AT.

Drive and disk manufacturers devised the perfect solution for this problem, short of using a redesigned controller. They built Into the drive a media sensor, which, when it is enabled, can override the controller's RWC signal (or lack of it) and properly change the head-current levels within the drive. Essentially, the drive chooses the write-current level Independently from the controller when the media sensor is operational.

The sensor is a small physical or optical sensor designed to feel, or ''see," the small hole on the high-density 3 l/2.1nch disks located opposite the write-enable hole. The extra hole on these high-density or extra-high density disk is the media sensor's cue that the full write-current should be used to recording. If an ED disk is detected, the ED drive enables the vertical recording heads. Low-density; disk do-not have these extra holes; therefore, when the sensor cannot see a media-sensor: hole, It causes the drive to record in the proper reduced write-current mode for a double density disk.

Some people, of course; foolishly attempt f6 override the function of these sensors by needlessly punching an extra hole in a low density disk to fool the drive's sensor into acting as though actual highdensity disk has bee instored. Several "con artist" companies have made a fast buck by selling media sensor hole –punchers to unwary or misinformed people. These “shyster” disk –punch vendors try to mislead you in to believing that no difference exists between the low and high density disk a legitimate high density disk. This, of course, is absolutely untrue: The high density disks are very different from lowdensity disks, the differences between the disk are explained in more detail later in this chapter.

Another reason that this hole-punching is needless is that if you want to record a high-density format on a low-density disk, you only have to remove the jumper from the drive that enables the media sensor. Removing the media sensor jumper still allows the drive to work properly for high-density disks, writing at the full write-current level, but' unfortunately also allows the higher write-current to be used on

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low-density disks as well because then the drive has no way of knowing the difference, If you really want to risk your data to low-density disks formatted as high-density disks, you can save yourself the cost of the 540 hole-punchers. Note that even if you attempt to format or record properly on a 720K disk, you. still will be working at the higher write-current and risk trashing the disk.

Many systems, including the IBM PS/3 series, Compaq, Toshiba laptops and many others with floppy controllers built into the motherboard, do not need 1.44M drives with media sensors. Their controllers have been fixed to allow the RWC signal to be sent to the drive even when the controller is sending the 250 kHz data rate. This setup allows for proper operation no matter what type of disk or drive is used, as long as the user formats properly. Because these systems do not have a media sensor policing users, they easily can format low-density disks as high-density disk regardless of what holes are on the disk. This has caused problems for users of the older PS/2 systems who accidentally formatted 720K disks as –1.44M disks. When passed to a system that has an enabled media sensor, the system refuses to read to read the disks at all because it is not correctly formatted. If you are having disk interchange problems, make sure that you are formatting your disks correctly.

The newer PS/2 and other high-end systems from other manufacturers (Hewlett Packard, for example use an active media sensor setup in which the user no longer has to enter the correct FORMAT command parameters to format the disk. In these systems the media sensor information is passed through the controller to the BIOS, which properly informs the FORMAT command about which disk is in the drive. With these systems, it is impossible for a user to accidentally format a disk incorrectly and it eliminates the user from having to know anything about the different disk media types.

Handling Recording Problems with 1.2M and 360K Drives The 5 1/4 inch drives have their own special problems. One major problem resulting in needless data destruction is that the tracks sometimes are recorded at different widths for different drives. These differences in recorded track width can result in problems with data exchange between different 5 1/4 inch drives.

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As shown in table 13.1, the recorded tack-width difference affects only the 5 1/4-inch drives because the 5 1/4 inch low density drives record a track width more than twice that of the 5 1/4 inch highdensity drives. This difference presents a problem if a high-density drive is used to update a low-density disk with previously recorded data on it. The high-density drive, even in 360K mode, cannot completely overwrite the track left by the 40-track drive. The problem occurs when the disk is returned to the person with the 360K drive because that drive sees the new data as “embedded” within the remains of the previously written track. The 360K drive cannot

To avoid this problem, start with a brand-new disk that has never been formatted and format it in the 1.2M drive with the/4 (or equivalent) option. This procedure causes the 1.23M drive to place the proper 360K format on the disk. The 1.2M drive the can be used to fill the disk to its 360K capacity and every file will be readable on the 40-track-360K drive because no previous wider data tracks exist to confuse the 360K drive, I use this trick all the time to exchange data between AT systems that have only a 1.2M drive and XT or PC systems that have only a 360K drive. The key is to start with a brand-new disk or a disk wiped clean magnetically by a bulk eraser. Simply reformatting the disk does not work because formatting actually writes data to the disk.

Note the because all the 3 1/2 inch drives write tracks of the same width, these drives have no diskinterchange problems related to track width.

CD – DVD DRIVE AND WRITER

CD – ROM The familiar audio compact disc is popular medium for storing music. In the computer world, however, the medium is called compact disc-read-only memory (CD-ROM). CD-ROM uses the same technology used to produce music CDs. If your computer has a CD-ROM drive, a sound card and speaker, you can play audio CDs on your PC

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A CS-ROM drive reads digital data (whether computer data or audio) from a spinning disc by focusing a laser on the disc’s surface. Some areas of the disc reflect the laser light into a sensor and other areas scatter the light. A spot that reflects the laser beam into the sensor is interpreted as a 1 and the absence of a reflection is interpreted as a 0.

Data is laid out on a CD-ROM disc in a long, continuous spiral. Data is stored in the form of lands, which are flat areas on the metal surface and pits, which are depressions or hollows a land reflects the laser light into the sensor (indicating a data bit of 1) and a pit scatters the light (in dicating a data bit of 0). A standard compact disc can store 650 MB of data or about 70 minutes of audio. A newer generation of compact discs, however, can hold 700 MB of data or 80 minutes of audio.

Compared to hard disk drives, CD-ROM drives are slow. One reason has to do with the changing rotational speed of the disk. Like a track on a magnetic disk, the track of an optical disk is split into sectors. However, the sectors are laid out differently than they are on magnetic disks.

DVD-ROM Many of today's new PCs feature a built-in digital video disc- read-only memory (DVD-ROM) drive rather than a standard CD-ROM drive. DVD-ROM is a high-density medium capable of storing a fulllength movie on a single disk the size of a CD. DVD-ROM achieves such high storage capacities by using both sides of the disc and special data-compression technologies and by using extremely small tracks for storing data. (Standard compact discs store data on only one side of the disc). The latest generation of DVD-ROM disc actually uses layers of data tracks, effectively doubling their capacity. The device's laser beam can read data from the first layer and then look through it to read data from the second layer. DVDs look like CDs. DVD-ROM drives can play ordinary CD-ROM discs. A slightly different player, the DVD movie player, connects to your

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Self Assessment Question

07. CD mean ______________ 08. DVD mean _____________ 09. What is a floppy? Answers: 07. Compact Disc. 08. Digital versatile disc. 09. Floppy is a storage device, which is used to store the data.

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UNIT – IV SYSTEM MAINTENANCE Computer systems are sturdy and fast, and they perform work easily and accurately. Under most operating conditions, computer systems are very reliable machines. But, like other machines, they wear out and fail. Computers do not burn out; they wear out or are forced out by human error or adverse operating conditions. While IBM Compatible Personal Computers have an excellent track record, the way in which you operate your machine and the environment in which you place it will influence directly the Mean Time Between Failures (MTBF). If you misuse your computer or do not protect it from the environmental elements, you can be the cause of its failure. Having once installed a computer system, some means of putting the system right in the event of failure, along with the possibility of diagnosing and correcting faults before they arise, must be considered. In addition to maintaining the system some form of back-up facilities should be arranged to cope in the event of a major equipment failure.

Consideration should be given to the maintenance of both hardware and software. Some installations may be sufficiently large to justify the employment of their own hardware engineers or to have a supplier's engineer permanently on-site. These installations are the exception rather than the rule and generally hardware maintenance is provided externally. A maintenance contract can be taken out either with the hardware supplier or with an independent third party. This contract is an alternative to paying for maintenance on a time and materials basis.

Hardware maintenance comprises an emergency call-out service and/or preventive maintenance cover. Similarly, software may be maintained either in-house or externally. A software maintenance contract can either be taken out with the supplier (if the software is bought-in), or with an independent third party (whether the software is bought-in, assuming availability of source code, or written in-house). Software maintenance comprises fault diagnosis/correction, enhancements and updates.

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Documentation One of the biggest problems in troubleshooting, servicing, or upgrading a system is proper documentation. As with the system units, IBM has set the standard for the type of documentation a manufacturer makes available. Some compatible manufacturers duplicate the size and content of IBM's manuals, and other manufacturers provide no documentation all. Generally, the type of documentation provided for a system is proportionate to the size of the manufacturing company. (Large companies can afford to produce good documentation.) Some of this documentation, unfortunately, is essential for even the most, basic troubleshooting and upgrading tasks. Other documentation is necessary only for software and hardware developers with special requirements. Types of Documentation Four types of documents are available for each system. Some manuals cover an entire range of systems, which can save money and shelf space. You can get the following types of manuals: Guide-To-Operations (GTO) manuals (called quick-reference manuals for the PS/2) Technical-Reference (TR) manuals Hardware – Maintenance Service (HMS) manuals Hardware – Maintenance Reference (HMR) manuals

A Guide-To-Operations manual is Included in the purchase of a system.

For PS/2 systems, these

manuals have been changed to Quick reference manuals. They contain basic instructions for system setup, operation, testing relocation, and opinion installation.

A customer-level basic diagnostics disk

(usually called a Diagnostics and setup Disk) normally is included with a system. ForPS/2 machines, a special disk – the reference Disk contains the setup and configuration programs, as well as both customer – level and technician-level diagnostics.

For PC and XT types of systems, you can find listings of all the jumper and switch settings for the motherboard. These settings specify the number of floppy disk drives, math-chip use, memory use, type

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of video adapter, and other items. For AT systems, the basic diagnostics disk also has the SETUP routine (used to set the date and time), Installed memory, installed disk drives, and Installed disk drives, and installed video adapters. This Information is saved by the SETUP program Into CMOS battery backed-up memory.

For PS/2 systems, the included disk (called the Reference Disk) contains the special

Programmable Option-Select (POS) configuration routine and a hidden and a version of advanced diagnostics. Technical-Reference Manuals The Technical-Reference manuals provide system specific hardware and software interface Information for the system. The manuals are intended for people who design hardware and software products to operate with these systems or for people who must integrate other hardware and software in to a system. Three types of Technical-Reference manuals are available: one is a Technical-Reference manual for a particular system; another covers all options and adapters; and a third covers the ROM BIOS interface. For PS/2 systems, one Hardware Interface Technical-Reference manual covers all PS/2 systems with updates for newer systems as they become available.

Each system has a separate Technical-Reference manual or an update to the Hardware Interface Technical-Reference manual. These publications provide basic interface and design Information for the system units. They indeed information about the system board, math coprocessor, power supply, video subsystem, keyboard, instruction sets, and other features of the system. You need this information integrating and installing after market floppy and hard disk drives, memory boards, keyboards, network adapters, or virtually anything you want to plug Into your system. This manual often contains schematic, diagrams showing the circuit layout it of the motherboard and pinots for the various connectors and jumpers. It also Includes listings of the floppy and hard disk drive tables which show the range of drives that can be Installed on a particular system. Power specifications for the power supply an also in this manual. You need these figures in order to: determine whether the system has adequate current to power a particular add-on device. The Options and Adapters Technical-Reference manual begins with a starter manual augmented with supplements. The basic manual covers a few IBM adapter cards, and supplements for new adapters and

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options are issued continually. These publications provide interface and design, information about the options and adapters available fur the various systems. This information includes a hardware description, programming considerations, interface specifications, and BIOS information.

The third manual is the BIOS. Interface Technical-Reference manual. This publication provides basic Input-output system (BIOS) interface information. This compendium covers every BIOS that has been available in IBM's systems. The manual is designed-for developers of hardware or software products that operate with the IBM PC and PS/2 products. Hardware-Maintenance Manuals Each hardware-maintenance library consists of two manuals; a Hardware-Maintenance Service manual and a Hardware-Maintenance Reference manual. These are real service manuals that are written for service technicians. Although their intended audience is the professional service technician, they are very easy to follow and useful even for amateur technicians or enthusiasts. IBM and local computer retail outlets use these manuals for diagnosis and service,

For IBM systems, two sets of manuals are available, One set covers the PC, XT, Portable PC, AT, and. PS/2 Model 25 an 1 Model 30. The other manual set covers the PS/2 systems except Model 25 and Model 30: these systems are considered old PC or XT systems, rather than true PS/2 systems. Manuals are purchased in starter from and then updated with supplements covering new systems and options. The PS/2 Model 25 and model 30, for example, are covered by supplements that update the PC maintenance Library. The basic Hardware-Maintenance Service manual for the PC or PS/2 contains all the information you need to trouble shoot and diagnose a falling system. This book contains special flowcharts that IBM calls Maintenance-Analysis Procedures (MAPs), which can help you find a correct diagnosis in 11 step-by-step manner. It contains Information about jumper positions and switch settings, a detailed parts catalog, and disks containing the advanced diagnostics. The Hardware-Maintenance Service manual Is an essential part of a trouble shooter's tool.

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Many technicians with trouble shooting experience never need to use MAPs. When they have a tough problem, however, MAPs help them organize a troubleshooting session. MAPs tell you to check the switch and jumper settings before the cables, to check the cables before replacing the drive or controller, and so on. This type of information is extremely valuable and can be generalized to a range of systems.

The basic Hardware-maintenance reference manual for the PC or PS/2 contains general information about the systems. It describes the diagnostic producers and Field-Replaceable Unit (FRU) location system adjustments, and component removal and installation. The information in it is useful primarily to users with no experience in disassembling and reassembling a system or to users who have difficulty identifying components within the system. Most people do not need this manual after the first time they take down a system for service.

Obtaining Documentation You cannot accurately troubleshoot or upgrade a system without a Technical-Reference manual. Because of the specific nature of the information in this type of manual, it will most likely have to be obtained from the manufacturer of the system. The IBM AT Technical Reference Manual, for example, is useless to a person with a Compaq Deskpro 486. A person with a Deskpro 486 must get the specific manual for thai mdi.riine from Compaq. A service manual is also a necessary item, but is not available from most manufactures. This type of manual is not nearly as system-specific as a Technical Reference manual; because of that, the service manuals put out by IBM worn well for most compatibles, Some information, such as the parts catalog, is specific to IBM systems and does not apply to compatibles, but most of the IBM service manuals have general information.

Many knowledgeable reviewers use the IBM Advanced Diagnostics, included with the HardwareMaintenance Service manual, as an acid test for compatibility. If the system truly is compatible, it should pass the tests with flying colors. (Most system pass). Many manufacturers do not have or sell a book or disk equivalent to the IBM Hardware-Maintenance Service manual. Compaq, for example, has a service

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manual, but does not sell it or any parts to anyone who is not a Compaq-authorized dealer. Servicing or upgrading these systems therefore is more costly, and limited by how much your dealer helps you. Buyers are fortunate that sufficient third-party diagnostics world with most compatible systems such as the Compaq systems.

To get hardware-service documentation, contact the dealer who sold you the system and then, if necessary, contact the manufacturer. (Contacting the manufacturer is often more efficient because dealers rarely stock these item). You can get any IBM manuals easily from IBM, To order the IBM manuals, call this toll-free number: 1-800-IBM-PCTB (1-800-426-7282)

TB is the abbreviation for Technical Books. The service is active Monday through Friday, from 8 a.m. to 8 p.m. Eastern time. When you call, you can request copies of the Technical Directory-a catalog listing all part numbers and, prices or available documentation. You also can inquire about the availability of technical-reference or service documentation covering newly announced products that might not be listed in the current directory.

The process of obtaining other manufacturers' manuals might (or might not) be so easy. Most larger-name companies run responsible service and support operations that provide technical documentation. Others either do not have or are unwilling to part with such documentation, to protect their service departments or their dealers' service departments from competition. Contact the manufacturer directly, and the manufacturer can direct you to the correct department so that you can inquire about this information.

SYSTEM TEARDOWN AND INSPECTION Using the Proper Tools To troubleshoot and repair PC systems properly, you need a few basic tools: Simple hand tools for basic disassembly and reassembly procedures Diagnostics software and hardware for testing components in a system

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Wrap plugs-for diagnosing serial And parallel port problems Test and measurement devices, such as Digital Multi-Meters (DMMs), that allow accurate measurement of voltage and resistance, and logic probes and pulsers that allow analysis and testing of digital circuits Chemicals, such as contact cleaners, component freeze sprays, and compressed air for cleaning the system. In addition, you might also need soldering and desoldering tools for problems that require these operations. These basic tools are discussed in more detail in the following section. Diagnostics software and hardware is discussed in Chapter 20, “Software and Hardware Diagnostic Tools”.

Hand Tools It becomes Immediately apparent when you work with PC systems that the tools required for nearly all service operations are very simple and inexpensive. You can carry most of the required tools in a small pouch. Even a top of the lines “Master mechanic’s” set fits inside briefcase-sized container. The cost of these tool kits ranges from about $20 for a small service kit $500 for one of the briefcase-sized deluxe kits.

Compare these costs to what might be necessary for an automotive technician. Most

automotive service techs spend between $5000 to $10,000, or more for the tools need Not only are the tools much less expensive, but I can ten-you from experience that you don't get nearly as dirty working on computers as you do when working on cars!

In this section, you learn about the tools required to make up a set capable of basic-level service on PC systems. One of the best ways to start such a set of tools is with a small kit sold especially for servicing PCs. This shows the basic tools you can find in one of the small “PC tool kits” sold for about $20: 3/16-inch nut driver ¼ inch nut driver Small Phillips screwdriver Small flat-blade screwdriver

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Medium Phillips screwdriver Medium flat-blade screwdriver Chip extractor Chip inserter Tweezers Claw-type pans graters T10 and T15 torx drivers

You use nut drivers to remove the hexagonal-headed screws that secure the system-unit covers, adapter boards, disk drives, power supplies, and speakers in most systems. The nut drivers work much better than a conventional screwdriver. Because some manufacturers have substituted slotted or Phillips bead screws for the more standard hexagonal head screws, the standard screwdrivers can be used for these systems. Your use the chip-extraction and Insertion tools to Install or remove memory chips for other, smaller chips) without bending any pins on the chip. Usually, you pry out larger chips, such as microprocessors or ROMs, with the small screwdriver. Larger processors, such as the 486 or Pentium chips, require a chip extractor if they are in a standard socket. These chips have so many pins on them that a large amount of force is required to remove them. The chip extractor tools for removing these; chips distribute the force evenly along the chip's underside to minimize the likelihood of breakage. The tweezers and parts grabber can he used to hold any small screws or jumper blocks that are difficult to hold in your hand. The parts grabber is especially useful when you drop a small part in to the interior of a system, usually, you can remove the part without completely disassembling the system. Finally, the Torx driver is a special, star-shaped driver that matches the special screws found in most Compaq systems, and in many other systems as well. Although this basic set is useful, you should supplement it with some other small hand tools, such as; Needle nose pliers Hemostats Wire cutter or wire stripper.

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Metric nut drivers Tamper-proof Torx drivers Vise or clamp File Small flashlight

Pliers are useful for straightening pins on chips, applying removing jumpers, crimping cables, or grabbing small parts.

Hemostats are especially useful for grabbing small components, such as jumpers.

The wire cutter or stripper obviously is useful for making or repairing cables or wiring.

The metric nut drivers can be used to remove Torx screws with the in tamper-resistant pin in the center of the screw. A tamper-proof Torx driver has a hole drilled in it to allow clearance for the pin.

You can use a vise to install connectors on cable and to crimp cables to the shape you want, as well as to hold parts during delicate operations. Finally, you can use the file to smooth rough metal-edges on cases end chassis, as well as to trim the faceplates on disk drives for a perfect fit.

The flashlight can be used to light up system interiors, especially when the system is cramped and the room lighting is not good. I consider this an essential tool.

Another consideration for your tool kit is an ESD (Electro Static Disnarge) protection kit. These kits consist of a wrist strap with a grounding wire, and a specially conductive mat also with its own ground-wire. Using a kit like this when working, on a system will help to ensure that you never accidentally zap any of the components with a static discharge.

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The ESD kits, as well as all the other tools and much more, are available from a variety of tool vendors. Specialized Products Company and Jensen Tools' are two of the more popular vendors of computer and electronic tools and service equipment. Their catalogs show an extensive selection of very high quality tools. These companies and several others are listed in Appendix B, “Vendor List,” With a simple set of hand tools, you will be equipped for nearly every PC repair or installation situation. The total cost for these tools should be less than $150, which is not much considering the capabilities they give you.

Soldering and Desoldering Tools For certain situations, such as repairing a broken wire, reattaching a component to a circuit board, removing and installing chips that are not in a socket, or adding jumper wire or pins to a board, you must use a soldering iron to make the repair. Even if you do only hoard-level service, you will need a soldering iron in some situations You need a low-wattage iron, usually about 25 watts. More than 30 watts generates too much heat and damage the components on the board. Even with a low-wattage unit you must limit in the amount of heat to which you subject the board and its components. You can do this with quick and efficient use of the soldering iron, as well as with the use of heat-sinking devices clipped to the leads of the device being soldered, A heat sink is a small, metal, clip-on device designed to absorb excessive heat before it reaches the component that the heat sink is protecting. In some cases a pair of hemostats can be used as an effective heat sink when you solder a component. To remove components originally soldered into place from a printed circuit board, you can use a soldering iron with a solder sucker. This device normally is constructed as a small tube with an air chamber and a plunger-and-spring arrangement. The unit is “cocked” when you press the spring-loaded plunger into the air chamber. When you want to remove a device from a board, you heat with the soldering iron the point at which one of the component leads joins the circuit board, from the underside of the board, until the solder melts. As soon as melting occurs, move the solder-sucker nozzle Into position and press .the actuator, This procedure allows the plunger to retract and to create a momentary suction that inhales the liquid solder from the connection and leaves the component lead dry In the hole.

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Always do the heating and suctioning from the underside of a board, not from the component side, Repeat this action for every component lead joined to the circuit board When you master this technique, you can remove .a small chip, such as a 16-pin memory chip, In a minute or two with only a small likelihood of damage to the board or other component. Larger chips with many pins can be more difficult to remove and resolder without damaging other components or the circuit board.

If you intend to add soldering and desoldering skills to your arsenal of abilities, you should practice. Take a useless circuit board and practice removing various components from the board; then reinstall the components. Try to remove the components from the board by using the least amount of heat possible. Also, perform the solder-melting operations as quickly as possible, and limit the time the iron is Applied to the joint. Before you install any components, clean out the holes through which the leads must project, and mount the component into place. Then apply the solder from the underside of the board, suing as little heart and solder as possible. Attempt to produce joints as clean the joints that the board manufacturer performed by machine. Soldered joints that do not look "clean" may keep the component from making a good connection with the rest of the circuit. This "cold-solder joint" normally is created because you have not used enough hear. Remember that you should not practice your new soldering skills on the motherboard of a system you are attempting to repair. Don't. attempted work on real boards until you are sure of your skills. I always keep a new junk board around for soldering practice and experimentation. No matter how good you get at soldering and desodering, some jobs are best left to professionals! For example, components that are surface mounted to a circuit board require special tools for soldering and desoldering, as do other components with very high pin densities. I upgraded my IBM P75 portable system by replacing the 486DX-33 processor with a 486DX2-66 processor. This would normally be a simple procedure (especially if the system uses a Zero Insertion Force or ZIF socket), but in this system the 168-pin 486DX chip is soldered into a special processor card! To ass to the difficulty, there were surface mounted components also on both sides (even the solder side) of the card. Well, needless to say, this was a very difficult job that required a special piece of equipment called a hot air rework station. The hot air rework station uses blasts of hot air to simultaneously solder or desolder all of the pins of a chip at

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once, To perform this replacement job the components on the solder side were protected by a special heat resistant masking tape and the hot air was directed at the 168 -pins of the 486 chip while the chip was pulled out from the other side. Then the new chip was placed in the holes In the board, a special solder paste was applied to the pins and the hot air was used again to simultaneously solder all 168 pins. The use of professional equipment like this resulted in a perfect fob that cannot be told from factory original and resulted to a perfectly operating66 MHz system. Attempting a job like this with a conventional soldering iron would have probably damaged the very expensive DX2 processor chip as well as the even more expensive multi layer processor card.

Self Assessment Question

01. System maintenance means _______________ 02. Maintenance tools are ________ ______________ _____________ 03. What is preventive maintenance.

Answers: 01. Trouble shooting and repairing PC System. 02. Multi-meter, Cleaning Chemical, hand tools. 03. It is a maintenance to obtain years & Trouble free service from your computer system.

Using Proper Test Equipment 1n some cases you must use specialized devices to test system board or component. This test equipment is not expensive or difficult to use; but can add much to your trouble-shooting abilities. I consider wrap plugs and a voltmeter required gear for proper system testing. The wrap plugs allow testing of serial and parallel ports and their attached cables. A Digital Multi-Meter (DMM) can serve many purposes, including checking for voltage signals at different points in a system, testing the output of the power supply and checking for continuity In a circuit or cable. An outlet tester is an invaluable accessory

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that can check the electrical outlet for proper wiring. This is useful if you believe the problem lies outside the computer system itself.

Logic probes-and pulsers are not considered mandatory equipment, but they can add to your troubleshooting proficiency; You use the logic probe to check for the existence and. status of digital signals at various points in a circuit. You use the logic pulser to inject signals into a circuit to evaluate the circuit operation. Using these devises effectively requires more understanding of how the circuit operates.

Wrap Plugs (Loop back Connection) For diagnosing serial and parallel-port problems, you need wrap plugs, also called loop back connection. Which are used to circulate, or “wrap�, signals. The plugs enable the serial or parallel port to send data to itself for diagnostic purpose. Several types of wrap plugs are available, you need one for the 25-pin serial port, one for the 9-pin serial port and one for the 25-pin parallel port (see table 3.1) Many companies, including IBM, sell the plugs separately and IBM also sells a special version that includes all three types in one plug.

Table 3.1 Wrap Plug Types Description

IBM Part Number

Parallel-port wrap plug

8529228

Serial-port wrap plug, 25-pin

8529280

Serial-port wrap plug, 9-pin (AT)

8286826

Tri-connector wrap plug

72x8546

The handy tri-connector unit contains all commonly needed plugs in one compact unit. The unit cost approximately 530 from IBM. Be aware that most professional diagnostics packages (especially the ones I recommend Include the three types of wrap plugs as part of the package; you may not need to

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purchase them separately. If you're handy, you can even make your own wrap plugs for testing. I have included wiring diagrams for the three types of wrap plugs in chapter II, communications and networking. In that chapter you will also find a detailed discussion of serial and parallel ports.

Meters Many troubleshooting procedures require that you measure voltage and resistance, your take these measurements by using a handheld digital multi-meter (DMM). The meters can be analog devises (using an actual meter) or digital readout devices. The DMM has a pair of wires, called test leads or probes. The test leads make the connections so that you can take readings, Depending on the meter’s setting, the probes will measure electrical resistance, Direct current (DC) voltage, or alternating-current (AC) voltage.

Usually each system-unit measurement setting has several ranges of operation. DC voltage, for example, usually can be read in several scales to a maximum of 200 mill volts, 2 volts, 20 volts, 200 volts and 1000 volts. Because computers use both +5 and +12 volts for various operations, you should use the 20-volt-maximum scale for making your measurements. Making these measurements on the 200-millivolt or 2-volt scales could “peg the meter” and possibly damage it because the voltage would be much higher than expected, using the 200-volt or 1000-volt scales works, but the readings at 5 volts and 12 volts are so small in proportion to the maximum that accuracy is low.

If you are taking a measurement and are unsure of the actual voltage, start at highest scale and work your way down. Some better system-unit meters have an autoranging capability-the meter automatically selects the best range for any measurement. This type of meter is much easier to operate. You just set the meter to the type of reading you want, such as DC volts and attach the probes to the signal source. The meter selects the correct voltage range and displays the value. Because of their design, these types of meters always have a digital display rather than a meter needle.

I prefer the small, digital meters. You can buy them for only slightly more than the analog style and they’re extremely accurate. Some are not much bigger than a cassette tape; they can fit in a shirt

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pocket. Radio Shack sells a good unit (made for Radio Shack by Beckman) in the $25 price range, which is-only a half-inch thick, weighs 3 1/2 ounces and is digital and autoranging as well. This type of meter works well for most if not all. PC troubleshooting and test uses.

You should be aware that many analog meters can be dangerous to digital circuits. These meters use a 9-volt battery to power the meter for resistance measurements. If you use this type of meter to measure resistance on some digital circuits, you can damage the electronics because you are essentially injecting 9volts into the circuit. The digital meters universally run on 3 to 5 volts or less.

Logic Probes and Logic pulsers A logic probe can be useful diagnosing problems with digital circuits. In a digital circuit, a signal is represented as either high (+5 volts) or low (0 volts). Because these signals are present for only a short time (measured in millionths of a second), or oscillate or switch on and off rapidly, a simple voltmeter is useless. A logic probe is designed to display these signal conditions earily

Logic probes are especially useful in troubleshooting a dead system. Using the probe, you can determine whether the basic clock circuitry is operating and whether other signals necessary to system operation are present. In some cases, a probe can help you crosscheck the signals at each pin on an 1C chip. You can compare the signals present at each pin to what a known, good chip of the same type would show-a comparison helpful in isolating a failed component. Logic probes can be useful in troubleshooting some disk drive problems by letting you test the signals present on the Interface cable or drive-logic board.

A-companion tool to the probe is the logic pulser.

A pulser is designed to test circuit reaction by

delivering into circuit a logical high (+5,volt) pulse, usually lasting 11/2 to 10 millionths of a second. Compare the reaction to that of a known functional circuit. This type of device normally is used much less frequently than a logic probe, but in some cases can be helpful in testing a circuit

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Self Assessment Questions

04. What is soldering? 05. What is meter? 06. Desoldering means ________ ________________

Answer: 04. It is the process of Reattaching the component to a board. 05. It is a hand held digital device used to trouble shooting 06. It is the process just opposite to soldering i.e., detaching the components from the board.

Drive Partitioning Partitioning a hard disk is the act of defining areas of the disk for an operating system to use as a volume. When you partition a disk, the partitioning software writes a master partition boot sector at Cylinder 0, Head 0, Sector 1-the first sector on the hard disk. This sector contains data that describes the partitions by their starting and ending cylinder, head, and sector locations. The partition table also indicates to the ROM BIOS which of the partitions is bootable and, therefore, where to look for an operating system to load. The FDISK program is the accepted standard for partitioning hard disk drives for use with all operating systems up through Windows Me. Windows 2000 and XP use a similar program called DISKPART. All versions of Windows starting with Windows 95 can also partition and format the drive using the SETUP program for installing the OS. These programs are included with your operating system, and although they might have the same name and basic functions with any OS, you should typically use the tools that

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specifically came with your OS. Partitioning prepares the boot sector of the disk in such a way that the FORMAT program or the Windows SETUP format utility can operate correctly.

Partitioning also enables various operating systems to coexist on a single hard disk. No matter which Operating system you use, it should come with an FDISK, DISKPART, or SETUP program that can be used to partition the drive. Because FDISK, DISKPART, and SETUP depend on BIOS information about the hard disk to determine the size and drive geometry of the hard disk, having correct BIOS settings saved in the BIOS Setup is vital to the correct operation of these programs. If a 100GB hard drive is defined in the BIOS as a 100MB hard drive, for example, all these programs will see us 100MB. With any version of Windows, as with MS-DOS, FDISK enables you to create two types of disk partitions: primary and extended. A primary partition can be bootable but and extended. A primary partition can be bootable but an extended partition can't. If you have only a single hard disk in your to start your computer from the hard disk (and who doesn't?). A primary system, at least part of the drive must be prepared as a primary partition if you want partition is seen as a single volume or drive letter (C: on one-drive systems), whereas an extended partition acts as a sort of logical container for additional volumes (drive letters D: and beyond). A single extended partition can contain a single volume (also referred to by FDISK as a logical DOS drive) or several volumes (logical DOS drives) of various sizes. Don't get hung up on the fact that FDISK calls partitions "DOS" partitions or "DOS" drives. This is true even though the operating system you are installing is Windows 95, 98, Me, NT, 2000, XP, Linux and so on. Depending on the version of Windows in use (and with any version of MS-DOS), you might need to subdivide a hard drive through the use of FDISK. The original release of Windows 95 and all MS-DOS versions support a file system known as FAT16, which allows no more than 65,536 files per drive and a single drive letter or volume size of no more than 2.1GB. Thus, a 10GB hard disk prepared with MS-DOS or the original Windows 95 (or 95A) must have a minimum of five drive letters and could have more.

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FORMATTING FORMAT Command Summary This section is a short guide to the DOS FORMAT command, with newer DOS versions supporting more and different types of disk hardware, the once-simple FORMAT command has become more complex, Especially with the advent of DOS V5.0, the number of-parameters and options available for the FORMAT command have increased dramatically. This section discusses the FORMAT command and these optional parameters. You see a simple guide to proper formatting of disks, as well as a thorough description of the FORMAT Command parameters and options.

This chapter emphasized that a specific disk must always be formatted to its designated capacity. Formatting a disk to a capacity different from what it was designed for results only in an eventual loss of data from the disk. Because all the. higher-density drives can format all the lower-density of the same form factor, knowing when a particular command option is required can be complicated. The basic rule is that a drive always formats in its native mode unless specifically instructed otherwise through the FORMAT command parameters. Therefore, if you insert a 1.44M HD disk in a 1.44M HD A drive, you then can format that disk by simply entering FORMAT A-no optional parameters are necessary in that case. If you insert any other type of disk (DD, for example), you absolutely must enter the appropriate parameters in the FORMAT command to change the format mode from the default 1.44M mode to the mode appropriate for the ferreted disk. Even though the drive might have a media sensor that can detect which type of disk is inserted in the drive, in most cases the sensor does not communicate to the controller or DOS, which does not know which disk it is. An exception to this is the 2.88M drive installations that support active media sense. Most 2.88M drive installations support this advanced feature, which means that the media sensor will communicate the type of the inserted diskette to the controller and DOS. In this case no parameters are ever needed when formatting diskettes no matter what type is inserted. The FORMAT command will automatically default to the proper type as indicated by the active sensors on the 2.88M drive. I have even seen 1.44M drive installations with active media sensing (certain Hewlett Packard systems, for example), but this is rare.

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In most cases of 1.44M drive installations; the media sensor in the drive is passive and in effect all the sensor does is force the FORMAT command to fail if you do not enter the correct parameters for the inserted disk type. IBM has licensed several third-party companies to produce industrial is of PS/2 system. Industrial systems usually use a different cooling-system from the one used in a regulated PC. A large cooling fan is used to pressurize the case rather than depressurize it, as most systems do. The air pumped into the case passes through a filter unit that must be cleaned and changed periodically. The system is pressurized so that no contaminated air can flow into it; air flows only outward. The only way air can enter is, through the fan and filter system. Fragmentation Fragmentation occurs when programs are stored on the disk and erased; then new programs are stored. If the new file is larger than the one previously occupying that space on the4 disk, the operating system may have to divide the new file and store it on different parts of the disk. Fragmentation slows down data retrieval and is hard on the disk drive. Running a defragmentation program reorganized the files on the disk so that each file is located in adjacent clusters on the disk. The reorganization speeds up data retrieval and helps prolong the life of the hard disk. Many programs are available to accomplish this task; operating systems often provide a built-in defragmentation program. SELF ASSESMENT QUESTIONS

07. Formatting means _____________ 08. What is partitioning? 09. What is fragmentation?

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UNIT - V SYSTEM POWER MAINTENANCE Using power-Protection Systems Power-protection systems do just what the name implies: they protect your equipment from the effects of power surges and power failures, In particular, power surges and spikes-can damage computer equipment, and a loss of power can result in lost data. In. this section, you learn about the four primary type so power-protection devices available and under what circumstances you should use them.

The power supplies in-IBM equipment are designed to provide protection from higher-than normal voltages and currents, and provide a limited amount of power line noise filtering.

Voltage drop to 80 volts for up to 2 seconds Voltage drop to 70 volts for up to .5 seconds Voltage surge of.up to 143 volts for up to 1 second

IBM also states that neither their power supplies nor syst ms will be' damaged by the following occurrences: Full power outage Any voltage drop (brownout) A spike of up to 2,500 volts Because of the high quality power supply design that IBM uses, they state in their documentation that external surge suppressors are not need for PS/2 system. Most other high quality name brand manufacturers also use high quality power supply designs.

Auto restart function.

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This type of power supply acts the same as others in a massive surge or spike situation it shuts down the system.

The following type of power protection devices are explained in the sections that follow. Surge suppressors Line candidatures Standby power supply (SPS) Uninterrupted power supply

Surge suppressors (protectors) The simplest from of power production is any of the commercially available surge protectors. Devices inserted between the system and the power line.

The only type of surge suppressors worth buying, therefore should have two features: conformance to the UL 1449 standard and a status light indicating when the MOVs are blow. Units that meet the UL 1449 specification say so on the packaging or directly on the unit. If this standard is not mentioned, it does not conform and you should avoid it.

Another good feature to have in a surge suppressor is built in circuit breaker that can be reset rather than a fuse. The breaker protects you system it the system of a peripheral develops a short. These better surge suppressors usually cost about.

Phone Line Surge Protectors In addition to protecting the power lines, it is critical to provide protection to sour systems from any phone lines that are connected. If you are using a modem of fax board which is plugged into to phone. system, any surges or spikes that level the phone line can po9tentiallyt damage your system. In many areas, the phone lines are especially susceptible to lightning strikes, which is the largest cause of fried modems and computer equipment attached to them.

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Several companies manufacture of sell simple protectors that plug between your modem and the phone line. These inexpensive devices can be purchased from most electronics supply houses.

Line Conditioners A line conditioner is designed to remedy a variety to problems. It filters the power, bridges brownouts, suppresses high-voltage and current conditions and generally acts as a buffer between the power line and the system. A line conditioner does the job of a surge suppressor and much more. It is more of an active device functioning continuously rather than a passive device that activates only when a surge is present. A line conditioner provides true-power conditioning and can handle myriad problems. It contains transformers, capacitors and other circuitry that temporarily can bridge a brownout or low voltage. These units usually cost several hundreds of dollars, depending of the power handling capacity of the unit.

Backup Power The next level of power protection includes backup power-protection devices. Self Assessment Questions

04. Power maintenance means _____________________ 05. UPS stands for ____________________ 06. What is power backup. Answer: 04. Taking care of the system by providing best possible electrical environment. 05. Uninterrupted power supply. 06. These units can provide power in care of a complete block out.

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Standby Power Supplies (SPS) A standby power supply is known as an off-line device if functions only when normal power is disrupted. An SPS system uses a special circuit that can sense the AC line current. If the sensor detects a loss of power on the line, the system quickly switches cyer to a standby battery and power inverter. The power inverter converts the battery power to 110-volt AC power, which then is supplied to the system. SPS systems do work, but sometimes a problem occurs with the switch to battery power. A truly outstanding SPS adds to the circuit a Ferro resonant transformer, a large transformer with the capability to store a small amount of power and deliver it during the switch time. SPS units also may not have internal line conditioning of their own; most cheaper units place your system directly on the regular power line under normal circum stances and offer no conditioning. SPS devices without the Ferro resonant transformer still require the use of a line conditioner of full protection. SPS systems usually cost from $200 to several thousands of dollars, depending on the quality and power-output capacity.

Switch Mode Power Suppliers (SMPS) PC power suppliers an of a switching rather that a linear design. The switching type of design uses a high speed oscillator circuit to convert the high wall – souckel AC voltage to the much lower DC voltage need to power PC and PC components. Switching type power supplier are noted for being efficient in size weight and energy in comparision to the linear design. The switching supply uses a switching circuit that chop up incoming power at a relatively high frequency. This enables the use of high frequency transformation that are much smaller and lighter. Also, the higher frequency is much easier and cheaper to filter out at the output and the input voltage can very kindly. Input ranging from 9oV to 135V still producers the proper output levels and moving switching suppliers can automatically adjunt to 220 V input. One characteristic switching type power suppliers is that donot run without a load. Therefore, your must have something such as a mother board and hard drive plugged in and drawing power lower for the supply to work. Most power suppliers are trotreted from non-load operation and shutdown automatically.

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Uninterruptible Power Supplies (UPS) Perhaps the best overall solution to any power problem is to provide a power source that is both conditioned and that also cannot be interrupted-which describes and uninterruptible power supply. UPSs are known as online systems because they continuously function and supply power to your computer systems. A true UPS system is constructed much the same as an SPS system. A battery charger connected to the line or wall current keeps the battery charged at a rate equal to or greater than the rate at which power is consumed. UPS cost is direct function of both the length of time it can continue to provide power after a line current failure and how much power it can provide.

Many SPS systems are advertised as though they were true UPS syytems. Because of a UPS’s almost total isolation from the line current, it is unmatched as line conditioner and surge suppressor. The best UPS systems and a Ferro resonant transformer for even greater power conditioning and protection capability. This type of UPS is the best form of power protection available. The price, however, can be very high. A true UPS costs from $1 to $2 per watt of power supplied.

TYPES OF UPS SYSTEMS Besides being characterised by output power capacity, uninterruptible power sources are generally configured in two ways continuously supply power to the computer with a continuous duty UPS or supply power only when the electricity fails, using a standby power. Here, the term UPS is used to describe both types of units, differentiating when necessary.

Continuous duty UPS A continuous duty UPS supplies power to the computer all the time. In this type, also called online UPS, 220V AC power is developed and supplied continuously to the computer by a static inverter, which gets its own power from a storage battery (or batteries) depending upon the power requirements.

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The battery charges itself continuously through the incoming utility power line (see Figure 17.3.3). Simultaneously, the inverters are synchronised to the utility line frequency of 50 Hz to eliminate any undesired effects upon the computer systems. Such an effect might be a beat frequency between the utility's power and the frequency of the power generated by the free-running static inverter.

FIGURE 17.3.3 In an on-line Uninterruptible Power Supplies, the Invertor always gets its DC Voltage from either the battery or the rectifier, eliminating interruptions caused by Switchover delays Under normal operation, the inverter frequency is maintained in power line sync via a phaselocked loop (PLL) circuit quite often operated in conjunction with a ferroresonant circuit, which may be thought of as a tuned inductance-capacitance oscillator. When the line power disappears, the inverter frequency drifts slowly to a preset 50 Hz. The line frequency must change gradually so as not to induce any transients. Similary, when power returns, the frequency of the inverter is gradually synchronised with the power company's line frequency. Many continuous duty UPSs are designed to switch the computer input connections back to the utility's power line when the inverter fails. Since the battery's DC voltage is always present at the inverter's input, the designer must either insert a time delay or add line-sensing circuitry at the charger or converter end. Doing so initiates the switch between AC rectified and battery based sources. A bypass switch sets up a direct connection to the AC line, should the battery or inverter fail or overload.

Standby UPS In the standby or switchover mode, the output of the battery-inverter is disconnected under normal line conditions, but the battery remains charged (see Figure 17.3.4). When the AC power fails, the line-sensing circuit activates the battery-inverter. A switchover typically takes 10 ms, with the load input actually seeing an interruption in the line for that period.

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Standby UPS systems are maintained in a ready state with their battery (or batteries) receiving a trickle charge. When the utility's power line voltage falls below a preset level, the inverter is switched on. A simple relay coil that detects the loss of power line voltage can trigger the switch. In other cases, very elaborate electronic sensing circuits can trigger the standby UPS, based upon parameters such as the absolute line voltage, the occurrence of the line transients, or whether the frequency and phase of the inverter are in sync with the decaying utility line voltage.

USING DATA-BACKUP SYSTEMS

Backup Policies All users and managers of computer systems should develop a plan of regular disk back ups. A backup interval should be selected based on the amount of activity on the system. Backups rarely must be scheduled at more than weekly intervals. Some users settle on a mixed plan: perform weekly disk backups and daily backups of only the changed files. The procedures for backing up and for dealing with copy protection are explained in the following section.

Backup Procedures You should back up to removable media such as cartridge or tape, which you remove from a system and store in a safe place. Backups performed on nonremovable media, such as another hard disk, are much more vulnerable to damage, theft, or fire; also, having multiple backups is much more expensive. These backup are raise backups. Perform your backups on a rotating schedule. One solution is to back up the drive using either an 8mm videotape drive or a 4mm digital audio tape (DAT) drive.

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Backup Systems A good, reliable backup is important when you’re using a large hard disk. Tape backup is available in configurations easily supporting hundreds of megabytes and more. Tape backup is fast and accurate. Basic parameters of different tape-backup devices include the following Type of media used Hardware interface Backup software These parameters are explained in the following sections. QIC Standards The Quarter-Inch Committee (QIC) issues standards for such things as tape-drive controller adapters; the tape cartridges and commands that tae drives understand. You will find them listed in Appendix B, the “Vendor List”. QIC standards, such as the SCSI command set in QIC-104 and QIC-123, which define data compression methods. Tape Media Media refers to the type of tape format used. The type of media you select dictates the capacity of the tape-unit storage. Many different types of systems use many different types of media, but I am concerned with only a handful of standard media types.

DC-600 cartridges DC-600 cartridge is a relatively large tape, 4 x 6 x 0.665 in L x W x D and has a heavy metal base plate. Many variations of the DC-600 tapes exist. DC-2000 cartridges This tape is 2.415 x 3.188 x 0.570 inches in L x W x D, with a heavy metal base plate.

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4mm DAT (digital audio tape) cartridges The recording technology is similar to digital audio tape decks and is dome in a Helical-Scan format; it is licensed by Sony (the original DAT developer). DAT tapes can hold as much as 1.3 gigabytes (1 gigabyte = 1.024M) 8mm cartridges These cartridges, which use the 8mm videotape developed by Sony. The recording is done physically as a Helical-Scan, the same method used in a video recorder.

Interfaces for Tape Backup Systems Of the three primary hardware-interface standards, virtually all professional backup systems use the QIC-02 (for Quarter-Inch committee 02) or SCSI (for small computer systems interface) and more recently, the parallel port interface. This connector saves the use of a slot in these systems. The data throughput of the SCSI interface is either SMB or 10MB per minute of standard and fast 8-bit SCSI respectively. These types of backup systems offer independence from a particular type of system; which is especially useful in a mixed machine or mixed bus environment. Other companies, like Trantor, offer parallel port SCSI adapter, to which you can connect any SCSI device including hard disk, CD-ROM, tape backup, scanners and so on.

Taps Backup Drivers And Software One type to software does not recognize the data formats of another proprietary software system. Other tape software packages are designed to run on a variety of tape hardware rather than a single manufacturer’s system. All of these products work with a number of different tape drives. All software should be capable of certain basic operations. Make sure that your software does what you want and consider buying only software that has these features. Can back-up and entire DOS partition (full volume backup) Can back up any or all files individually (file-by-file backup)

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Allows a selective file-by-file restore from a volume backup as ess as a file-by-file backup Can combine several backups on a single tape Can run the software as commands from DOS BATCH files Works under a network Can span a large drive on multiple tapes Can be completely verified

Physical Location: Internal or External Physical location of the tape-backup units is a simple factor often not considered in detail. I almost never recommend any tape-backup unit mounted internally in a system unit. I recommend that you buy a tape unit externally mounted in its own chassis and one that connects to the system unit through a cable and connectors.

Recommended Backup System Although a variety of backup systems are available. I recommend units from any manufacturer that meets these requirements: Type of media:-DC-2000, DC-600, 4mm DAT, on 8mm Hardware interface: QIC-02, Parallel port or SCSI The parallel port adapters make it easy to use a single external DAT drive to back up a variety of systems.

Developing a Preventive Maintenance Program This type of preventive maintenance primarily involves periodic cleaning of the system and its components. Using power-protection devices. clean, temperature-controlled environment, and preventing excessive vibration Cleaning a System One of the most important operations in a good preventive main prouder. Dust buildup on the internal components can lead to several problems. One is that dust acts as a thermal insulator which prevents

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proper system cooling. One problem that can develop is overheating. The buildup of dust acts as a heat insulator, which prevents the system from cooling properly.

Disassembly and Cleaning Tools Contact cleaning solution Canned air A small brush Lint-free foam cleaning swabs Antistatic wrist-grounding strap

You might also want to acquire these optional items Foam tape Low-volatile room-temperature vulcanizing (RTV) sealer Silicone type lubricant Computer vacuum cleaner

Chemicals Standard Cleaners Contact Cleaner-Lubricants Dusters Many specific chemicals are used in cleaning and dusting solutions, but five types are of particular interest. The EPA has classified ozone-damaging chemicals into tow classes: Class I and Class II, Chemicals that fall into these two classes have their usage regulated other chemicals are no regulated, class I chemicals include. Chlorofluorocarbons (CFCs) Chlorinated solvents

Standard Cleaners Standard cleaning solutions are available in available of types and configurations. You can use pure isopropyl alcohol, acetone, Freon, trichloroethane, or a variety of other chemicals. The material must be moisture-free and residue-free.

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Contact Cleaner/Lubricants These are very similar to the standard cleaners but include a lubricating component. The lubricant coating also acts as a conductive protectant that insulates the contact from corrosion. Dusters Compressed gas often is used as an aid in system cleaning. Originally these dusters used CFCs such as Freon, while modern dusters now use HFCs or carbon dioxide\, neither or which is damaging to the ozone layer. Vacuum Cleaners Canned gas is usually better for cleaning in small areas. A vacuum cleaner is more useful when you are cleaning a system loaded with dust and dirt.

Brushes and Swabs A small brush (makeup, photographic, or paint) can be used to carefully loosen accumulated dirt and dust before spraying with canned air or using the vacuum cleaner. Use cleaning swabs to wipe off electrical contacts and connectors, disk drive heads and other sensitive areas. Using the foam tape rather than the RTV because it is easier and neater to apply. The low-volatile RTV also eliminates the bad vinegar smell. The low-volatile RTV is available from most auto-supply stores. Silicone Lubricants Silicone lubricants are used to lubricate the door mechanisms on floppy disk drives and any other part of the system that may require clean, non-oily lubrications. Always use the silicone sparingly. Obtaining Required Tools and Accessories Most cleaning chemicals and tools can be obtained from a number of electronics supply houses, or even the local Radio Shack.

Disassembling and Cleaning Procedures To properly clean your system, it must at leas be partially disassembled.

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All plug-in adapter cards must be removed along with the disk drives.

Reseating Socketed Chips As your system heats and cools it expands and contracts and the physical expansion and contraction causes components plugged into sockets to gradually work their way out of those sockets. This process is called chip creep. First, clean the dust and debris on the board and then clean any connectors on the board. The duster are especially effective at blasting any dust and dirt off the boards. Also blow any dust out of the power supply, especially around the fan intake and exhaust areas. You do not need to disassemble the power supply to do this, just a duster can and blast the compressed air into the supply through the fan exhaust pore. This will blow the dust out of the supply and clean off the fan blades and grille which will help with system airflow.

Cleaning Connectors and Contacts Cleaning the connectors and contacts in a system promotes reliable connections between devices. On a motherboard, you will want to clean the slot connectors, power-supply connectors, keyboard connector, and speaker connector.

Cleaning Floppy Drives Floppy Disk Drives and Controllers explains the procedure for cleaning floppy drives, the information is not repeated here.

Cleaning the Keyboard and Mouse Keyboards and mice are notorious for picking up dirt and garbage.

This usually does not require complete disassembly of the keyboard.

Most mice are easily cleaned.

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Hard Disk Maintenance Certain preventive maintenance procedures proton your data and ensure that your hard disk works efficiently

Decrementing Files Over time, as you delete and save files to a hard disk, the files become fragmented. This means that they are split into many noncontiguous areas on the disk.

Passive Preventive Maintenance Procedures Passive preventive maintenance involves taking care of the system in and external manner: basically, providing the best possible environment-both physical as well as electrical-for the system to operate in. Physical concerns are conditions, such is ambient temperature, thermal stress from power cycling, dust and smoke contamination and disturbances such as shock and vibration. Electrical concerns are items such as electrostatic discharge (ESD), power line noise and radio-frequency interference. Each of these environmental concerns is discussed in this section.

Examining the Operating Environment One of the most overlooked aspects of microcomputer preventive maintenance is protecting the hardware and the sizable financial investment is represents from environmental abuse. Computer are relatively forgiving and they generally are safe in an environment that is comfortable for people. The environmental temperature should be as constant as possible. Keep your system away from radio transmitters or other sources of radio frequency energy.

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Self Assessment Questions

04. System tools are ______ ______ _______ 05. What is checking? 06. What is repairing? Answer: 04. Nut driver, head screw driver, needle nose pliers. 05. Examining the system. 06. Diagnosing the problem and correcting it.

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UNIT QUESTIONS

UNIT-I Section – A 1. What is personal computer? 2. What is central processing unit? 3. What is input device? 4. Mother board – explain 5. What is hardware? Section - B 6. Explain different types of PCs. 7. Write short notes on memory unit. 8. What is processor! Explain 9. Write the importance of motherboards? Section - C

10. Neatly explain about computer history. 11. What are main components of a Pc? Explain 12. What is Bus architecture? Explain.

UNIT-2

Section A

1. What is a mouse ? 2. What is a keyboard?

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3. Enumerate the difference between OMR & OCR. 4. What is Game controller? 5. Memory unit – explain. Section – B 6. Write short notes on keyboards. 7. Bring about to advantages of touch screen

.

8. What is web camera? Explain it’s advantages. 9. Give some idea

about digital camera.

Section C 10. Explain about computer peripherals. 11. What is monitor? Explain its types. 12. Pinpoint the difference between semiconductor memories and magnetic memories. UNIT-3

Section - A 01. Enumerate the difference between impact printer and non impact printer 02. What is a printer? 03. What is a plotter? 04. What is a sound card? 05. What is an optical drive?

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Section - B 06. Write about notes on multimedia devices 07. Neatly explain about audio output devices. 08. Where sound card is used? Explain. 09. Differentiate the term floppy disc from C.D.

Section - C 10. Explain the different types of printers. 11. Explain about plotter types. 12. What is CD/ DVD drive? Explain.

UNIT-4 Section - A 01. What is preventive maintenance? 02. What is meter? 03. Logic pulser - Explain? 04. What is partitioning? 05. What is fragmentation?

Section - B 06. Write about notes on hand tools. 07. What is the purpose of using meter? Explain. 08. Explain format procedure. 09. Desoldering tools Explain.

Section - C 10. Neatly explain about system maintenance. . 11. Bring out the importance of maintenance and tools. FOR MORE DETAILS VISIT US ON WWW.IMTSINSTITUTE.COM OR CALL ON +91-9999554621


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12. Explain partition neatly.

UNIT-5 Section – A 01. What is system maintenance? 02. What is power backup? 03. What is UPS? 04. What is the use of inverter?

Section - B 05. Write notes on inverter. 06. What are the advantages of checking? 07. Why UPS are used? Explain

Section - C 08. Explain preventive maintenance syntax. 09. Explain about system tools.

.,

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I NTRODUCTI ONOFCOMPUTERS

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IMTS DCA (Introduction of computers)  

IMTS DCA (Introduction of computers)

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