Chapter 04Form Factors and Power Supplies
Form Factors and Power Supplies In this chapter you will learn: About different form factors and computer
cases How electricity is measured How to protect your computer system against damaging changes in electrical power How to troubleshoot electrical problems
Computer Case, Motherboard and Power Supply Form Factors-pg.132 ď Ž Form Factor: describes the size, shape
and major features of a hardware component ď Ž Chassis: another word for computer case
Types of Form Factors-pg.133 BTX, ATX, LPX, NLX, Backplane Systems
and the outdated ATX Most Common: ATX, MicroATX, BTX and NLX
AT Form Factor Sometimes called “Full AT” Measures at 12” x 13.8” Supplies the system with +5, -5, +12, -12
Volts DC P8 and P9 Power Connector
Baby AT Form Factor pg.134 Smaller version of the AT form
factor Backwards compatible with the AT form factor Used from 1993 to 1997
ATX Form Factor Most commonly used today Developed in 1995 by Intel Better position of components Reduced potential of EMI (Electro
magnetic interference) Measures 12” x 9.6” so its smaller that an AT motherboard
ATX Form Factor The first ATX power supplies and
motherboards used a P1 power connector Provide the computer with: -3, +3, -5, +5, -12, +12 volts of DC current P1 connector uses 20 pins and ATX ver.2.2 uses 24 pins Power supplies with the extra 4 pins are also called ATX12V
MicroATX Form Factor pg.137 Variation of the ATX Reduces cost by reducing I/O ports Smaller power supply Smaller case
BTX Form Factor BTX (Balanced Technology Extended) Designed by Intel to be used by everything
big and small Takes full advantage of SATA, USB 2.0 and PCI Express Use a 24 pin power connector Improved wind tunnel effect pg.138
LXP and Mini-LPX Form Factors Developed by Western Digital One expansion slot with a riser card or
bus riser or daughter card Uses low profile cases and slim line cases Can only use the manufacturers power supplies
NLX Form Factor ď Ž Low end personal computer motherboard
developed by Intel in 1998 ď Ž Improvement over LPX
Backplane Systems Do not use a true motherboard Active backplanes contain bus connectors,
buffer and driver circuits Passive backplanes contain not circuitry at all Used for rack mounted systems Built for easy access
Types of cases pg.140 Desktop cases Tower cases
Desktop Cases Desktop case doubles as a monitor stand Low end desktops: compact cases, low-
profile cases or slim line cases Use the NLX, LPX and Mini-LPX form factor
Tower Cases Tower cases can be as high as two feet Often used for servers Good for upgrading Use the ATX, Mini-ATX and BTX form
factors
Notebook Cases ď Ž Proprietary- Can only be purchased from
the vendor. Example: Dell, Toshiba, Sony etc. ď Ž All are different in size and power supply, no set standards.
Measures and Properties of Electricity pg.143
AC and DC AC-Alternating Current AC goes back and forth (oscillates) at
60Hz or 60 times in one second Alternates from -110v to +110v
AC and DC
DC-Direct Current Travels in only one direction Most electronics use DC A rectifier converts AC to DC like in a power supply A transformer changes the amount of current A power supply uses a rectifier and a transformer
Hot, Neutral and Ground pg.144 Hot-the hot connector is the source of the
electricity Neutral-the neutral connectors is the path back to the power station for the electricity Electricity flows from Hot to Neutral Ground is an escape route for out of control electricity like in a short
Hot, Neutral and Ground Fuses ď Ž Fuses are rated in AMPS ď Ž They are made to prevent too much current from flowing through a circuit
Receptacle Tester ď Ž A receptacle tester is used to verify that
hot, neutral and ground are wired correctly
Some Common Electrical Components pg.146 ď Ž Transistor- serves as a gate or a switch for
an electrical signal and can amplify the flow of electricity.
Some Common Electrical Components Capacitor- an electronic device that can
hold an electrical charge for a period of time and can smooth the uneven flow of electricity through a circuit. Used in power supplies Can be dangerous even when unplugged
Some Common Electrical Components ď Ž Diode-allows electricity to flow in only one
direction. ď Ž One to four diodes in various configurations is called a rectifier and is used to convert AC to DC
Some Common Electrical Components Resistor- a resistor limits the amount of
current that can flow through it. Used to protect a circuit from over load Resistors are color coded to indicate the level of resistance measured in Ohms
DC
Fuse
Capacitor
Wall Outlet
Diode
Resistor