Three Ways Settings Can Be Stored on a Motherboard

When setting hardware configurations, you can configure the motherboard in three different ways: DIP switches, jumpers, and CMOS. Storing configuration information by physically setting DIP switches or jumpers on the motherboard or peripheral devices is inconvenient, because it often requires you to open the computer case to make a change. However, many older and some newer motherboards require that you set certain configurations using DIP switches and jumpers, as outlined below.
Setup Data Stored by DIP Switches
Many older computers and a few newer ones store setup data using DIP switches on the motherboard, as shown in the figure below. A DIP (dual inline package) switch has an ON position and an OFF position. ON represents binary 1 and OFF represents binary 0. If you add or remove equipment, you can communicate that to the computer by changing a DIP switch setting. When you change a DIP switch setting, use a pointed instrument such as a ballpoint pen to push the switch. Don�t use a graphite pencil, because graphite conducts electricity. Pieces of graphite dropped into the switch can damage it.
Setup Data Stored by Jumpers
Most motherboards use at least one set of jumpers, such as the set shown below. If two pins are not connected with a cover, the setting is considered OFF. If the cover is present, the setting is ON. If the cover is hanging on one pin, it is parked so you won't lose it. You can see all three situations shown below. A 6-pin jumper group on a circuit board (a) has no pins covered, (b) has a cover parked on one pin, and (c) is configured with two jumpers capped or covered.
A typical setting that uses jumpers is enabling or disabling keyboard power-up. (With this feature enabled, you can press a key to power up the system.) You change the jumper setting by removing the computer case, finding the correct jumper, and then either placing a metal cover over the jumper or removing the cover already there. The figure below shows a diagram of a motherboard with the keyboard power-up jumper. For older motherboards, typical uses of jumpers were to indicate the presence of cache memory or to communicate the type and speed of the CPU present.

Setup Data Stored in CMOS RAM
Computers today store most configuration information in a CMOS RAM chip, which also is called the real-time clock/nonvolatile RAM (RTC/NVRAM) chip, which retains the data even when the computer is turned off. (There are actually many CMOS chips on a motherboard, used for various purposes.)
On older computers (mostly IBM 286 PCs built in the 1980s), changes are made to the CMOS setup data using a setup program stored on a floppy disk. One major disadvantage of this method, besides the chance that you might lose or misplace the disk, is that the disk drive must be working before you can change the setup. An advantage of this method is that you cannot unintentionally change the setup. If you have an older computer and you do not have the floppy disk with the setup program, check the Web site of the motherboard manufacturer or the BIOS manufacturer for a replacement disk.



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