Best I can explain is like this. The cmos controls the input and output
of the mobo. Whether it be a raid config, or a ide config, or both. Whether
a pci-e video, versus pci, or even agp. It controls your ram timings, and
sees what quantity of ram you have, it monitors heat, fan rpm,, the whole
gamut of hardware function. When you build a new machine, the more often
then not need to clear cmos, the set up cmos as per your system specs.
Alot of times if your machine locks up, and you cant figure out what to do
clearing cmos is a good idea... Having a button to clear cmos is kinda
handy, but using the jumper on the mobo is not really a problem.