Download PC System Boards

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Chapter 2: PC System Boards
Introduction
This chapter covers the motherboard areas of the CompTIA A+ Certification—
Essentials examination under Objective 1.1. The system board is the main component in a PC-compatible microcomputer system. The system board contains
the components that form the basis of the computer system. Even though the
system board’s physical structure has changed over time, its logical structure has
remained relatively constant. Since the original PC, the system board has contained the microprocessor, its support devices, the system’s primary memory
units, and the expansion-slot connectors.
Technicians must be aware of the characteristics of different types of system
boards in the marketplace. This will enable them to make intelligent choices
about repairing, upgrading, or exchanging system boards.
System Board Form Factors
Although the term form factor generally refers to the physical size and shape of
a device, with system boards it also refers to their case style and power supply
compatibility, as well as to their I/O connection placement schemes. These factors must be considered when assembling a new system from components, and
in repair and upgrade situations where the system board must be replaced.
One of the first considerations when installing or replacing a system board is
whether it will physically fit (form factor) and work with the other system components (compatibility). In both of these situations, the following basic issues
must be dealt with: the system board’s form factor, its case style, and its powersupply connection type.
NOTE
CompTIA’s 2006 A+ exam deals only with ATX, BTX, and NLX form factors.
ATX System Boards
Intel developed the ATX form factor for Pentium-based systems as an evolution
of the older Baby AT form factor that first integrated the standard I/O functions
onto the system board. It has been the predominant PC form factor for some
time. The ATX specification basically rotates the Baby AT form factor by 90
degrees, relocates the power-supply connection, and moves the microprocessor
and memory modules away from the expansion slots.