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How to Clear Your Computer’s CMOS to Reset BIOS Settings

load-optimized-defaults

Your computer stores low-level settings like the system time and hardware settings in its CMOS. These settings are configured in the BIOS setup menu. If you’re experiencing a hardware compatibility issue or another problem, you may want to try clearing the CMOS.

Clearing the CMOS resets your BIOS settings back to their factory default state. In most cases, you can clear the CMOS from within the BIOS menu. In some cases, you may have to open your computer’s case.

Use the BIOS Menu

The easiest way to clear the CMOS is from your computer’s BIOS setup menu. To access the setup menu, restart your computer and press the key that appears on your screen – often Delete or F2 – to access the setup menu.

If you don’t see a key displayed on your screen, consult your computer’s manual. Different computers use different keys. (If you built your own computer, consult your motherboard’s manual instead.)

Within the BIOS, look for the Reset option. It may be named Reset to default, Load factory defaults, Clear BIOS settings, Load setup defaults, or something similar.

Select it with your arrow keys, press Enter, and confirm the operation. Your BIOS will now use its default settings – if you’ve changed any BIOS settings in the past, you’ll have to change them again.

load-setup-defaults-in-bios

Use the CLEAR CMOS Motherboard Jumper

Many motherboards contain a jumper that can be used to clear CMOS settings if your BIOS is not accessible. This is particularly useful if the BIOS is password-protected and you don’t know the password.

The exact location of the jumper can be found in the motherboard’s (or computer’s) manual. You should consult the manual for more detailed instructions if you want to use the motherboard jumper.

However, the basic process is fairly similar on all computers. Flip the computer’s power switch to off to ensure it’s not receiving any power. Open the computer’s case and locate the jumper named something like CLEAR CMOS, CLEAR, CLR CMOS, PASSWORD, or CLR PWD – it will often be near the CMOS battery mentioned below. Ensure you’re grounded so you don’t damage your motherboard with static electricity before touching it. Set the jumper to the “clear” position, power on your computer, turn it off again, set the jumper to the original position – and you’re done.

motherboard

Image Credit: Eden Richardson

Reseat the CMOS Battery

If your motherboard does not have a CLEAR CMOS jumper, you can often clear its CMOS settings by removing the CMOS battery and replacing it. The CMOS battery provides power used to save the BIOS settings – this is how your computer knows how much time has passed even when it’s been powered-off for a while – so removing the battery will remove the source of power and clear the settings.

Important Note: Not all motherboards have removable CMOS batteries. If the battery won’t come loose, don’t force it.

First, ensure the computer is powered off and you’re grounded so you won’t damage the motherboard with static electricity. Locate the round, flat, silver battery on the motherboard and carefully remove it. Wait five minutes before reseating the battery.

cmos-battery-in-laptop

Image Credit: John Lester


Clearing the CMOS should always be performed for a reason – such as troubleshooting a computer problem or clearing a forgotten BIOS password. There’s no reason to clear your CMOS if everything is working properly.

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.

  • Published 12/24/12

Comments (17)

  1. NSDCars5

    I have to be grounded? *runs to mom and says “Mum, ground me if you can! :P” mum says “you’re grounded”* *runs off to motherboard, fries his motherboard with static electricity*

  2. Jaybee

    Quite a few of the towers I’ve done this on take a few seconds after moving the CMOS clear jumper and restoring power to completely clear the CMOS. Most of those would signal the end of the cycle with a ‘beep’. The units were all commercial workstations.

  3. Max

    any solution for laptop? i forgot its bios password?

  4. Hans

    Hello,

    Can someone help me out? After the BIOS was flashed (updated), I encountered lots of problems. The most persisting one seems to be: I cannot start from any CD/DVD anymore. Consequently I cannot perform a reinstall of Windows 7 etc. No matter the boot sequence, it simply doesn’t work anymore. Also, an external CD/DV RW doesn’t work.

    Been looking for a solution for 2 months now. This once seems one I came across earlier but not so well explained.

    Could this help solve the mentioned DVD/CD/USB boot failure? Is there any risk of resetting it?

    Thanks.
    Hans Boutkan
    The Netherlands

  5. Randy

    As far as laptops go I found only thing that would clear my CMOS password on my old Toshiba (forget model). CMOS Cleaner (http://www.pccmos.com/)

    You can’t just take a battery out of a laptop as most CMOS batteries in laptops are soldered in. I could have sent it to toshiba with proof of ownership and over $100 to have them clear it. At that point if I couldn’t have got it cleared I would have spend few hundred dollars more on another laptop rather than pay for password to my OWN computer.

  6. Miky

    First off – read your manual(s) before performing any hardware work – with that said always keep your paperwork, receipts, and manuals. Next I’m getting a call for help… Always backup any data, Always use antistatic solutions prior to touching your hardware…. To many times friends and or co-workers read articles like this and think hey that will fix this issue with out taking the time to think before jumping in… have fun – but be smart and safe about it….

  7. Tom

    Answer to Hans:

    I think you really need to try to take the CMOS Battery out like in this article. I think that it should be able to detect your media for Windows 7. Also do you know how to set boot sequence to your CD/DVD Rom drive that has your installation disc?

    There is also a manual for your system if you have a retail PC. There is normally a factory disc that you can use in order to restore your PC to factory (default) settings on your systems. This would be your next best solution as you do not to worry about issues since you are starting fresh.

    This happened to my yesterday 12.23.12 with trying to overclock my PC with a messed up voltage settings. My PC would not start so I took out the CMOS Battery and waited for a few minutes and the PC I was using booted up without issues.

    Miky is also correct. You do need to try to back up your data once or twice a week to protect your data if you need to reinstall Windows.

    I hope some of my advice helps you although I think it is 19:25 (24.12.12) your time.

  8. fab

    on many motherboards and laptops you can also reset the bios to default setup by pressing the key while powering it up

  9. debsawyer

    Fab,

    What is ‘the key’?

  10. JWC

    to fab
    you did not mention “WHAT KEY” in your post for resetting the laptop?

  11. Hans

    Hello Miky and Tom,

    Thans for the replies and suggestions.

    First of all, I make a daily scheduled backup both to the cloud and external hard drive.
    I will ask a pro support engineer from dell to come by and try this battery issue. I am partly disabled and incurable sick als a result of which I can’t do this myself.

    A question that pops up is: what can happen if I succeed to reset the BIOS? Would / could it mess up the system even more?

    All BIOS settings seem OK. I can load the BIOS and check it all. Also, I can see the boot sequence and change it anyway I won’t to but it doesn’t matter; it keeps on booting from the HD.

    Again, thanks for your help and have a great day ahead.

    Kind regards,

    Hans
    The Netherlands

  12. Rick

    UNPLUG hardware before working on it to be truly safe – power off switch is insufficient. BTW, years ago on an old laptop, there was a way to clear the BIOS Password by shorting two pins on the Printer port, which was only documented in a tech manual not a regular user manual. Saved having to open the case.

  13. jonathan

    would this fix a fan running at the wrong speed?

  14. hudahel

    @hans please check this out, maybe it can help you.
    maybe the HD is the one thats prio on your boot loader if you will change it to dvd/cd maybe it will work. =)

    http://www.howtogeek.com/129815/beginner-geek-how-to-change-the-boot-order-in-your-computers-bios/

  15. Nelson

    Hans;
    Control Panel > Device manager >
    1) @ DVD / CD-ROM Drives: Delete ALL drives here. (say YES when asked)
    2) @ IDE ATA/ATAPI Controllers: Delete ALL here. (again…YES)
    (and … YES..THIS DOES TAKE A LEAP OF “FAITH”..)
    3) Close Device Manager and back out to Desktop.
    4) Reboot the device..and Windows WILL find and reinstall EVERYTHING again.
    5) Check the CMOS settings just to be sure of all settings,and be sure to check the / turn on the Secondary Master & Slave IDE Settings too. (if these were NOT turned on..reboot after it’s done.)

    Now you should have use of all Drives and be able to re-install everything you need to do.

    The reason I know it will work is that I have had to do the very same thing to FINALLY to be able to use my drive after three months driving the Dell Techs and everybody else crazy..because all of my BIOS settings and all of the “other” settings were standard “Factory” settings…but my drives would not work..I even changed them both out and still nothing…but they do today!!
    (NO–Nobody told me how to do this either…it was my “last Ditch” effort!!)
    (And this was AFTER resetting my CMOS with Battery removal too.)

    Happy Hunting!!

  16. xcylone

    Under what circumstances should I want to clear the CMOS?

  17. Viggenboy

    Hmmm wonder if this will help my daughter’s dead Acer netbook, which won’t even let me access the general bios, acts like bios isn’t even there. But of course being a netbook, no CD to bot from and – without access to BIOS can’t force it to boot from somewhere else (i.e. USB )

    Anyone with any clues advice on this I’ love to hear from you

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