Datasheet

Identifying Components of Motherboards 9
Peripheral ports and connectors
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BIOS
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CMOS battery
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Jumpers and DIP switches
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Firmware
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In this subsection, you will learn about the most-used components of a motherboard,
what they do, and where they are located on the motherboard. We’ll show what each com-
ponent looks like so you can identify it on most any motherboard you run across. Note,
however, that this is just a brief introduction to the internal structures of a computer. The
details of the various devices in the computer and their impact on computer service prac-
tices will be covered in later chapters.
FIGURE 1.3 Components on a motherboard
Keyboard connector (KEYBD)
USB connectors (USB0, USB1)
Serial port connector (COM1)
Parallel port connector (PARALLEL)
MIDI/game port connector (GAME)*
Auxiliary line-in audio connector (AUX IN)*
* For systems with onboard audio
ISA expansion card connector
(ISA1 and ISA2)
PCI expansion card connectors
(PCI1, PCI2, PCI3, PCI4)
Modem audio cable connector for using
audio system as speaker phone (TELPH)*
CD-ROM drive audio cable connector (CD)*
Onboard audio controller jacks
(LINE OUT, LINE IN, and MIC IN)*
Mouse connector (MSE)
Power input connector (POWER)
Microprocessor fan
connector (J4M1)
Chassis cooling fan connector (J8M1)
3.3-V power input connector (3.3)
Diskette drive interface connector (FLOPPY)
Control panel connector (J8H1)
Secondary EIDE channel connector (SEC IDE)
Accelerated graphics port connector (AGP)
Battery socket (B7C1)
Configuration jumper (J8A1)
Speaker (U8A1)
DIMM sockets (BANK 0, BANK 1, BANK 2)
Primary EIDE channel connector (PRI IDE)
SCSI hard disk drive access indicator
cable connector (J8J1)
Microprocessor SEC cartridge connector (J4J1)
Bus Architecture
Many components of a computer system work on the basis of a bus. A bus, in this sense, is
a common collection of signal pathways over which related devices communicate within the
computer system. Expansion buses of various architectures, such as PCI and AGP, incorpo-
rate slots at certain points in the bus to allow insertion of external devices, or adapters, into
the bus, usually with no regard to which adapters are inserted into which slots; insertion is
generally arbitrary. Other buses exist within the system to allow communication between
the CPU and other components with which data must be exchanged. Except for CPU slots
and sockets and memory slots, there are no insertion points in such closed buses because no
adapters exist for such an environment.
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