Datasheet
Identifying Components of Motherboards
33
from electrostatic discharge (ESD). Another ramification is that it doesn’t take much of a
power source to keep CMOS chips from losing their contents.
To prevent CMOS from losing its rather important information, motherboard manu-
facturers include a small battery called the CMOS battery to power the CMOS memory.
The batteries come in different shapes and sizes, but they all perform the same function.
Most CMOS batteries look like large watch batteries or small, cylindrical batteries. Today’s
CMOS batteries are most often of a long-life, nonrechargeable lithium chemistry.
Jumpers and DIP Switches
The last components of the motherboard we will discuss in this section are jumpers and
DIP switches. These two devices are used to configure various hardware options on the
motherboard. For example, some motherboards support processors that use different core
(internal) and I/O (external) voltages. You must set the motherboard to provide the cor-
rect voltage for the processor it is using. You do so by changing a setting on the mother-
board with either a jumper or a DIP switch. Figure 1.26 shows both a jumper set and DIP
switches. Motherboards often have either several jumpers or one bank of DIP switches.
Individual jumpers are often labeled with the moniker JPx (where x is a unique number for
the jumper).
FIGURE 1.26 Jumpers and DIP switches
Jumper Rocker-type DIP switch Slide-type DIP switch
Many of the motherboard settings that were set using jumpers and DIP
switches are now either automatically detected or set manually in the BIOS
setup program.
Firmware
Firmware is the name given to any software that is encoded in hardware, usually a read-
only memory (ROM) chip, and can be run without extra instructions from the operating
system. Most computers and large printers use firmware in some sense. The best example of
firmware is a computer’s BIOS routine, which is burned in to a chip. Also, some expansion
cards, such as small computer system interface (SCSI) cards and graphics adapters, use their
own firmware utilities for setting up peripherals.
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