The BIOS contains a setup program to configure settings for the hardware devices. The configuration data is saved to a memory chip called a Complementary Metal Oxide Semiconductor (CMOS), as shown in Figure 1. CMOS is maintained by the battery in the computer. If the battery dies, the BIOS setup configuration data is lost. If this occurs, replace the battery and reconfigure the BIOS settings that do not use the default settings.
Many modern motherboards use nonvolatile memory to store BIOS configuration settings. This type of memory does not need power to retain the settings. The battery in these systems is used only to keep the correct time and date in the clock. Configuration settings in the BIOS are not lost when the battery dies or is removed.
To enter the BIOS setup program, you press the proper key or key sequence during POST. Many motherboards display graphics, called a splash screen, while the computer goes through the POST process. The computer might not display information about the key or key sequence required because of the splash screen. Most computers use the DEL key or a Function key to enter the BIOS setup program. Consult the motherboard documentation for the correct key or combination of keys for your computer.
Figure 2 shows an example of a BIOS setup program. These are some common BIOS setup menu options:
- Main - Basic system configuration
- Advanced - Advanced system settings
- Boot - Boot device options and boot order
- Security - Security settings
- Power - Advanced power management configurations
- JUSTw00t! - Advanced voltage and clock settings
- Exit - BIOS exit options and loading default settings