How to Reset the BIOS on a Computer

The Basic Input/Output System (BIOS) is motherboard firmware that initiates all computer hardware components. The BIOS enables the adjustment of various system and hardware settings. Default factory BIOS settings guarantee that the system will be stable and bootable. Inappropriate or extreme changes of BIOS parameters to achieve, for instance, hardware overclocking may destabilize your computer or even prevent the system from booting. CMOS (complementary metal--oxide--semiconductor) is an integrated motherboard chip that stores current BIOS settings and is powered up from the battery. If a computer will not boot due to prior changes of BIOS setting, clearing CMOS is a way to reset the BIOS.

Instructions

Removing the CMOS Battery

1. Switch off the computer.

2. Open the computer case. This is typically achieved by removing the side panel. Then lay the computer on its side.

3. Locate the CMOS battery that is placed in the socket approximately in the center of the motherboard. The CMOS battery is round and flat, and about 1/2 inch in diameter.

4. Lift the CMOS battery out of its socket and set it aside on a piece of paper. Wait 5 to 20 minutes.

5. Insert the CMOS battery back into its socket.

6. Close the side panel, and press the power button to switch the computer on.

Using a CMOS Jumper

1. Switch off the computer.

2. Open the computer case. This is typically achieved by removing the side panel. Then lay the computer on its side.

3. Find the "CMOS clear" jumper on the motherboard. Such a jumper is usually located near the CMOS battery socket, which is approximately in the center of the motherboard. This jumper is a small 2-pin shunt installed over the 3-pin connector. In the default position, the jumper is usually placed over the first and second pins of the connector.

4. Remove the jumper from the 3-pin connectors using your fingers or a small forceps.

5. Place the jumper over the second and third pins of the connector. This is the CMOS clearing position. Wait 10 to 20 seconds.

6. Remove the jumper from the 3-pin connectors again, and reinstall it in the default position over the first and second pins of the connector.

7. Close the side panel, and press the power button to switch the computer on.

Using the BIOS Setup

1. Consult your computer/motherboard manual or online resources (see Resources) to determine the key to access the BIOS. Typically, it is a Delete, F1, F2 or F10 key.

2. Press the reset button to restart your computer.

3. Press the key identified in Step 1 as soon as the computer or motherboard manufacturer's logo appears on the screen in order to enter the BIOS setup.

4. Navigate to the BIOS option "Exit" using the arrow keys on your keyboard. Then select "Load Default Setting" and press Enter.

5. Press F10; the computer will be automatically restarted, and the BIOS will be reset to the factory default settings.

Tips & Warnings

• It is highly advisable that you consult the motherboard manual to find the exact location of the CMOS jumper (Section 2). If you are unable to find the jumper or are unsure if it is the right one, follow the instructions in Section 1.

References

• The BIOS Companion: The Book That Doesn't Come With Your Motherboard;" P. Crouncher; Dec. 17, 2004

Resources

• Motherboard Support Links
• Motherboard BIOS Access Keys