CMOS means Complementary Metal-Oxide-Silicon. On older computers, the CMOS is powered by a battery.

Newer systems have a rechargeable accumulator. The CMOS battery varies with the age of your computer and the type of motherboard. Some CMOS batteries look like little coins. Others are soldered onto the motherboard.

How Does A Computer Keep Time?

Computers keep time. They keep a steady beat like a good drummer in the band. Every computer has a real-time clock. It runs 24 hours a day, 7 days a week whether the computer is turned on or not.

 

Your computer uses the CMOS to count the clock cycles. The real-time clock increments a counter 18.2 times each second. Your operating system—Windows VIsta, for example—converts that counter into hours, minutes and seconds.

The CMOS does more than keep time

Your computer also has a number of low-level configuration settings stored on the motherboard. The BIOS or Basic Input Output System holds information about your CPU, RAM, even how many hard drives are in your computer. Without the BIOS, your computer wouldn’t know where to begin. The BIOS settings are also stored in the CMOS.