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what does the cmos battery do

 Did you know that there is a battery in your computer's motherboard? Here's what a CMOS motherboard battery does and why you need it.

If you are using an older desktop or laptop your computer's motherboard has an integrated battery. But unlike a standard laptop battery, the motherboard battery does not turn on the computer while you are using it.

On the contrary in fact - the battery is tiny and active only when you are not using your computer.

So why is there a battery in the motherboard and what is it for? How long does a battery last? Let's find out.

What Is a CMOS Battery?

CMOS represents complementary metallic-oxide semiconductors. In the early days of PCs, CMOS RAM (volatile memory type) retained the BIOS settings.

CMOS RAM requires a battery Otherwise the settings will be lost when the computer is turned off.

Modern computers no longer use CMOS RAM. They store the BIOS settings in non-volatile memory which means the settings do not need to maintain constant power.

Meanwhile, modern UEFI motherboards save settings to flash memory or the computer's hard disk drive. There is no need for a battery in these systems but you will often find it anyway.

CMOS Battery and Its Use

A CMOS battery provides backup power to a computer's (Complementary metal-oxide-semiconductor) to maintain certain parameter values for example: RTC (real-time clock). 

These key parameters will be used when the system restarts. Many computers use CMOS memory to hold the current time and date. 

The CMOS memory and clock circuit that increases the time it is powered by a small battery called RTC so that the time is updated properly even when the computer is disconnected.

The CMOS memory can also contain the configuration parameters such as which disk to boot from. CMOS is used because it draws so little power that the battery installed in the original factory usually lasts several years. 

However, when it starts to fail the computer can show that it has diseases and forgets things it has known for years like from which hard disk to boot.

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