Motherboards also include a small separate block of memory made from CMOS RAM chips which is kept alive by a battery (known as a CMOS battery) even when the PC’s power is off. This prevents reconfiguration when the PC is powered on.
CMOS devices require very little power to operate.
The CMOS RAM is used to store basic Information about the PC’s configuration for instance:-
Floppy disk and hard disk drive types
Information about CPU
RAM size
Date and time
Serial and parallel port information
Plug and Play information
Power Saving settings
The Other Important data kept in CMOS memory is the time and date, which is updated by a Real Time Clock (RTC).
Fuente: https://patkay.hubpages.com/hub/the-motherboard-components
