Understanding BIOS, CMOS, and Firmware

You know what the CPU does—it does the “thinking” for the computer. But, how does the CPU “know” what kinds of drives are connected to the computer? What tells the CPU when the memory is ready to be read or written to? What turns on the USB ports or turns them off? The answer to all these questions is the BIOS. Next to the CPU, the BIOS chip is the most important chip found on the motherboard. Figure 7-1 illustrates the location of the BIOS chip on some typical systems.

Figure 7-1. BIOS chips and CMOS batteries on typical motherboards.