When you turn on your computer, the CPU has no idea what to do with itself until it loads some kind of instructions. But it can't load an operating system, such as Windows, until it knows how to read the disk drive where the operating system code is stored. The BIOS (basic input/output system) is your computer's solution to the problem of starting itself without outside help.
The BIOS is a small block of software that your computer uses to test and configure its memory, disk drives, and other hardware, and to start the process that loads the operating system. Early computer designers called this process "pulling the computer up by its bootstraps," or booting the system.
The integrated circuit that contains the BIOS is an electrically erasable programmable read-only memory (EEPROM) that permanently stores the program until it receives a special command to erase and rewrite the program's code. This erasable function (also called flash memory) makes it possible to update the BIOS without physically replacing the BIOS chip. The BIOS EEPROM is mounted on the motherboard and communicates with the chipset (the set of integrated circuits that handles communication between the computer's processor and the other components).
Almost all BIOS chips contain code produced by two companies: Phoenix and AMI (American Megatrends). Award is another common brand, but that is owned by Phoenix. However, some large computer companies use private label versions that carry their name instead of the BIOS maker. The name of the BIOS maker usually appears on the BIOS chip, often with a version number. However, if the BIOS has been updated, the version number does not match the current version of the code stored on the chip.
This chapter discusses how the BIOS works, how to change the BIOS configuration settings, how to interpret the results of the Power-On Self Test, and also how to find and install updated versions of the BIOS software.