- Sep 17, 2010
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There are several ways to do this and it depends on your motherboard model. Always do this with your computer turned off, and unplug the power to make sure it is off.
For laptops, pull out the CMOS battery. It's usually reachable by opening a compartment on the bottom, but sometimes it will be under the keyboard. After you take it out, put it back in! Check out the videos below if you need an example:
http://www.youtube.com/watch?v=cg_wvp1YdSI
http://www.youtube.com/watch?v=MTg8qhWKNpA
For desktops you may have more options, depending on the motherboard model. Read your motherboard manual if you are unsure.
- You could pull out the CMOS battery. Just pop it out gently with a flat head screwdriver. Wait a minute, then put it back in.
- Moving a jumper switch. These should be designated in your motherboard manual. Move the jumper from position 1-2 to position 2-3. Then put the jumper back to position 1-2.
- Short the CLR CMOS leads with a screwdriver. Self explanatory. Consult your motherboard manual to confirm the location of these leads. Touch a small flathead screwdriver to both leads at once for a few seconds and you have done it.
- CMOS Clear button. Some newer motherboards have a button to press. It might be called debug or something other than CMOS CLR. It might be located on the rear output panel, or neat the case switch headers. It should show clearly in your motherboard manual exact location.
^^The methods above will usually work, but sometimes a capacitor on the motherboard will hold a charge on the BIOS IC. No problem, just remove the CMOS battery, and with the power cord unplugged, try pressing the power button. I have also seen very stubborn motherboards need to have the CMOS battery removed and just left off overnight to "drain" that pesky capacitor.
Last resort: I've ever had to do this two times in 18 years of working on electronics. Some BIOS ICs are not soldered into the motherboard and can be removed easily with some small pliers. They actually make a tool for this but chances are that you won't have one so just use small pliers like needlenose are fine. Remove that BIOS IC. Touch all of its leads to something conductive at once. Plug it back in. I don't know of any other way to clear your CMOS, but if someone else does, PM me and I will add it to this FAQ and credit your name with a quote.
For laptops, pull out the CMOS battery. It's usually reachable by opening a compartment on the bottom, but sometimes it will be under the keyboard. After you take it out, put it back in! Check out the videos below if you need an example:
http://www.youtube.com/watch?v=cg_wvp1YdSI
http://www.youtube.com/watch?v=MTg8qhWKNpA
For desktops you may have more options, depending on the motherboard model. Read your motherboard manual if you are unsure.
- You could pull out the CMOS battery. Just pop it out gently with a flat head screwdriver. Wait a minute, then put it back in.
- Moving a jumper switch. These should be designated in your motherboard manual. Move the jumper from position 1-2 to position 2-3. Then put the jumper back to position 1-2.
- Short the CLR CMOS leads with a screwdriver. Self explanatory. Consult your motherboard manual to confirm the location of these leads. Touch a small flathead screwdriver to both leads at once for a few seconds and you have done it.
- CMOS Clear button. Some newer motherboards have a button to press. It might be called debug or something other than CMOS CLR. It might be located on the rear output panel, or neat the case switch headers. It should show clearly in your motherboard manual exact location.
^^The methods above will usually work, but sometimes a capacitor on the motherboard will hold a charge on the BIOS IC. No problem, just remove the CMOS battery, and with the power cord unplugged, try pressing the power button. I have also seen very stubborn motherboards need to have the CMOS battery removed and just left off overnight to "drain" that pesky capacitor.
Last resort: I've ever had to do this two times in 18 years of working on electronics. Some BIOS ICs are not soldered into the motherboard and can be removed easily with some small pliers. They actually make a tool for this but chances are that you won't have one so just use small pliers like needlenose are fine. Remove that BIOS IC. Touch all of its leads to something conductive at once. Plug it back in. I don't know of any other way to clear your CMOS, but if someone else does, PM me and I will add it to this FAQ and credit your name with a quote.
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