CMOS SETUP, Configuration Data And How It Is Stored

Configuration Data And How It Is Stored

During the boot process, the Startup BIOS and operating system must determine what hardware is present. This information is called configuration data, setup data, or simply setup, and the settings are stored in the computer in one of the following devices: DIP switches, CMOS setup chips, or jumpers.

Setup Data Stored By DIP Switches

A DIP switch is similar to a light switch and is on or off based on the direction the small switch is set. Most systemboards have at least one, often several, jumpers and perhaps a single bank of DIP switches, although the trend is to include most setup information in CMOS rather than to have a jumper or switch on the board that has to be mechanically set.

A DIP switch (dual in-line package) is a switch that has an ON 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 sharp instrument, such as a ball-point pen, to push the switch, as shown in the figure below. DO NOT use a graphite pencil because graphite conducts electricity and broken pieces can drop into the switch and damage it.

Setup Data Stored On A CMOS Chip

Most configuration settings in newer computers are stored in a battery-powered CMOS chip. CMOS chips require very little electricity to retain data. Electricity from a battery enables the CMOS chip to hold the data even while the computer is off. The battery that powers the CMOS chip may be on the systemboard or attached nearby.

You can access the CMOS setup by pressing a specified key during the boot process. A message, similar to the following usually, appears on the screen. Press DEL to change Setup or Press F8 for Setup

The setup screen appears and usually has menus and help features to help you configure the system. When exiting the program, you are prompted to exit or to save your changes and exit.

Setup Data Stored By Jumpers

A jumper is a sleeve that connects a pair of vertical pins on a circuit board. The jumper serves as an electrical connection on the systemboard. If the pins are not connected with a cover, the setting is considered OFF. If the cover is present, the setting is ON.

Jumpers are used to communicate a variety of information to the computer. For example, on a PC, jumpers are used to select I/O addresses and IRQs. On an IDE drive, a jumper selects between master and slave. A jumper can be used in place of a more costly DIP switch. 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.