System BIOS support

Every system BIOS has two types of hardware to support. First, the system BIOS supports all of the hardware that never changes, such as the keyboard. (You can change your keyboard, but you can’t change the keyboard colltroler built into the Southbridge.) Another example of hardware that never changes is the PC speaker (the tiny one that beeps at you, not the play music). The system ROM chip stores the BIOS for these and other devices that never change.

          Second, the system BIOS supports all of the hardware that might change from time to time. This includes RAM (you can add RAM), hard devices (you can replace your hard drive with a larger drive or add a second hard drive, and floppy devices (you can add another floppy drive, although that’s not common today). The system ROM chip stores the BIOS for these devices, but the system needs another place to store information about the specific details of a piece of hardware. This enables the system to differentiate between a Western Digital Caviar Black 1.5-TB hard drive and a Seagate Barracuda 60-GB drive, and yet still support both drive right out of the box.