Abit IT5A User Manual page 33

Introduction to BIOS 3-3
CMOS DATA
Maybe you have heard somebody saying that their CMOS
DATA was lost. What is the CMOS? Is it important? The
CMOS is the memory used to store the BIOS parameters that
you have configured. This memory is passive. You can read its
data and you can also store data in it. But this memory has to
be powered by a battery in order to avoid any loss of its data
when the computer is turned off. Since you may have to
change the CMOS battery when it is out of power and in doing
so, you will loose all CMOS data, therefore, we recommend
that you write down all the parameters of your hardware, or to
put a label with these parameters on your hard disk.