as two floppy disk drives and two hard disk drives or
any combination thereof, depending upon the particular
configuration of your system. You would also see
several boards (also referred to as cards). Some boards
are used to control the peripheral devices of the system,
while other boards work in conjunction with the
microprocessor that is located on the system or
motherboard itself. These boards provide the flexibility
to add a variety of capabilities to a basic system. Certain
boards are required, such as the system board that
contains the main microprocessor(s). Others you might
add to control a light pen or mouse device, or to handle a
communications interface.
Looking inside the computer system unit (figure
1-8), you will notice there are 5 available slots for board
insertion. These various boards are plugged into what is
called the motherboard. The motherboard is a printed
circuit board that transmits the power and electronic
signals between the other boards and peripheral
devices. It is mounted to the bottom of the chassis of the
computer, as shown in figure 1-9. Memory chips, on the
newer micros, called single in-line memory modules
(SIMMs), are located on the motherboard in a group of
4 or 8 slots. In older micros the memory chips are
located on a memory expansion board. Most
microcomputers also have a lithium battery installed on
the motherboard. It provides power to the real-time
clock when the system is turned off. The life
expectancy of this battery is 3 to 5 years. Other boards
you are likely to see in a typical microcomputer are the
disk controller board, SCSI adapter board, and
video display board (figure 1-9). We will take a look at
each.
SLOT A—SCSI ADAPTER BOARD.— The
small computer systems interface (SCSI) adapter board
is used to control peripheral equipment, such as a CD-
ROM drive.
SLOTS B, D, E, F, AND H.— Slots B, D, E, F, and
H on this particular micro are reserved for future use.
SLOT C—DISK CONTROLLER BOARD.—
Most disk controller boards are capable of supporting
two internal hard disk drives, two internal floppy drives,
and one external magnetic tape drive for tape backup.
SLOT G-VIDEO DISPLAY BOARD.— The
video display board includes graphics memory chips to
provide the system with graphics capabilities. Most
micros come from the factory set for VGA (video
graphics array) settings.
By now, you should have a pretty good idea of what
you can expect to see inside the system unit in the way
of microcomputer boards. Before installing any
internal components within the system unit, you must
first carefully remove the outer cover. Be sure you are
authorized to make such changes before removing the
cover.
However, before you go looking for a
screwdriver, read the owner’s manual very carefully,
paying particular attention to the section on cover
removal and the steps to follow. For example, the
owner’s manual might say: “Once all cabinet screws
have been removed, raise the cover, keeping it as high as
Figure 1-9.—Boards within the microcomputer system unit and their locations.
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