The CMOS Battery
The CMOS Battery¶
The CMOS Battery is indeed a battery on a motherboard. This battery is reserved for our small block made from CMOS RAM chips. So, when our computer is turned off, the ROM component is not. This prevents our settings such as hard disk drive types, information about the processor, RAM size, data and time, serial and parallel port information, plug and play information, and power saving settings from resetting upon startup. Without this each time we would turn on the computer, configuration would be required1.
The battery is not in use when you are using the computer. It lasts somewhere between two to ten years (on average five years). Without this battery our system is vulnerable as it can refuse to boot the operating system, keeps shutting down without any user input, time and data are wrong all the time, or you need to configure them each time you turn your computer on. A wrong configuration will not allow you to connect to the internet. The BIOS will give you a constant beeping signal to inform you about the issue and it will not stop until the battery is replaced. Some of other errors include the computer having problems finding a printer, or random error messages that pop up on the screen2.
Unfortunately, this battery is not rechargeable and thus it is certain that it will run out at some point. But it has a separate circuit on the motherboard that prevents accidental discharge. However, once it runs out, all we need to do is to replace the battery and configure everything again3.
