A Complementary metal-oxide-semiconductor (CMOS) battery is a battery that gives power to the CMOS memory chip. CMOS is a non-volatile RAM that functions whether your computer is powered on or off. It also gives power to the basic input/output system (BIOS) so the CMOS chip can store its configuration settings.
CMOS batteries typically last for about ten years and use three to six volts of electricity. Two important characteristics of CMOS’s are that they use a low amount of power and also have a very high resistance to noise immunity; this can vary depending on the system and environment the PC is placed.
The function of a CMOS battery is to power the CMOS chip. The CMOS itself stores information such as the system’s time, date, and hardware settings. Hardware settings are typically configured in the BIOS of your computer. The primary function on BIOS is to set up the hardware and load and start an operating system.
These settings can involve configuring hardware and setting up the computer’s system clock, as well as enabling or disabling system components. BIOS also enables you to set up devices that are eligible to be a potential boot device and set up various password prompts. One example would be a password for securing access to the Bios user interface (BIOS UI) WHICH function themselves and prevent an unauthorized user from booting the system from unauthorized peripheral devices.
Different methods of clearing the CMOS Battery
- The easiest and fastest way to clear the CMOS battery involves going to BIOS Setup utility and choosing to “Reset BIOS settings” to their factory default levels. The option menu could defer with different motherboards, but it should display the following options: Reset to Default, Factory Default, Clear BIOS, Load Setup Defaults, etc. This particular option is usually available at the bottom portion of your BIOS options. This method will not reset the time and date, but will reset any user changes made in the BIOS.
- Another way you can clear the CMOS is by using the Motherboard Jumper. This chip is usually located near the CMOS battery or the BIOS chip. Once you switch the jumpers, turn your computer on and make sure the password has been cleared. Then, turn off your computer and replace its jumper back to its original positions.
- Also valid is reseating the CMOS battery by removing it and then reinstalling it. This would remove the source of power that saves your computer’s BIOS settings. You should wait two to three minutes before you reinstall the battery back to your system. Use this method if you can’t access the BIOS and you can’t locate the clear CMOS jumper.
- Alternatively users can clear the CMOS battery using a tool called CMOS De-Animator. It is a service utility for your system’s CMOS RAM to clear either the BIOS password or restore its password. This method will not reset the time and date, but will reset any user changes made in the BIOS. The first time you run this program, you are required to give one-time activated administrator privileges.
This program supports both 32 and 64-bit Windows operating systems except Windows 95 and NT 3.51. It does not currently support Mac or Linux operating systems. It also automatically detects what operating systems you have, and it includes a self-test on its start-up to ensure whether the CMOS is accessible or not. Once the check is completed, the program is ready for use.