Bringing BIOS to the PC

A talented programmer could write BIOS for a keyboard if the programmer knew the keyboards codebook; keyboard are pretty simple devices. This begs the question: where would this support programming be stored? Well, programming could be in-corporated into the operating system. Storing programming to talk to the hardware of your PC in the operating system is great-all operating system have built-in code that knows how to talk to your keyboard, your mouse, and just about every piece of hardware you may put into your PC.

          That’s fine once the operating systems up and running, but what about a brand new stack of parts you’re about to assemble into a new PC? When a new systems being built, it has no operating. The CPU must have access to BIOS for the most important hardware on your PC: not only the keyboard, but also the monitor, hard devices, optical-media drives, USB ports, and RAM. This code can’t be stored on a hard drive or CD-ROM disc-these important devices need to be ready at any time the CPU calls them, even before installing a mass storage device or an operating system.

          The perfect place to store the support programming is on the motherboard. That settles one issue, but another looms: what storage medium should the motherboard use? DRAM won’t work, because all of the data would be erased every time the computer was turned off. You need some type of permanent program storage device that does not depend on other peripherals to work. And you need that storage device to sit on the motherboard.