Clearing the CMOS: A Comprehensive Tutorial for Reinitializing System BIOS

Clearing the CMOS on your motherboard will reset your BIOS settings to their factory defaults, the settings that the motherboard maker decided were the ones that most people would use.

How to Clear CMOS

Below are three very different ways to clear CMOS. Any one method is as good as any other but you may find one of them easier, or whatever problem you might be having may restrict you to clearing the CMOS in a particular way.

Reset CMOS With the “Factory Defaults” Option

The easiest way to clear the CMOS is toenter the BIOS setup utility and choose toReset BIOS Settings to their factory default levels.

The exact menu option in your particular motherboard’s BIOS may differ but look for phrases like_reset to default_ ,factory default ,clear BIOS ,load setup defaults , etc. Every manufacturer seems to have their own way of wording it.

The BIOS Settings option is usually located near the bottom of the screen, or at the end of your BIOS options, depending on how it’s structured. If you’re having trouble finding it, look close to where the_Save_ or_Save & Exit_ options are because they’re usually around those.

Finally, choose to save the settings and then restart the computer.

The directions linked above detail how to access your BIOS utility but don’t specifically demonstrate how to clear the CMOS in your BIOS utility. It should be easy enough, however, as long as you can find that_reset_ option.

Clear CMOS by Reseating the CMOS Battery

Dell Inc.

Another way to clear CMOS is to reseat the CMOS battery. By disconnecting and then reconnecting the CMOS battery, you remove the source of power that saves your computer’s BIOS settings, resetting them to default.

Start by making sure your computer is unplugged. If you’re using a laptop or tablet, make sure the main battery is removed, too.

Next,open your computer’s case if you’re using a desktop PC, or find and open the small CMOS battery panel if you’re using a tablet or laptop computer.

Every laptop is different. Some may have a small battery compartment with its own cover, but many don’t. Instead, it may be in the same compartment where you will find the hard drive(s) and/or RAM chips and/or Wi-Fi radio(s). Sometimes you will need to remove the whole back cover.

Finally, remove the CMOS battery for a few minutes and then put it back in. Close the case or battery panel and then plug in, or reattach the computer’s main battery.

Laptops & Tablets: The CMOS battery shown here is wrapped inside a special enclosure and connects to the motherboard via the 2-pin white connector. This is an increasingly common way that manufacturers of small computers include a CMOS battery. Clearing CMOS, in this case, involves unplugging the white connector from the motherboard and then plugging it back in.

Desktops: The CMOS battery in most desktop computers is much easier to find and looks like a standard cell-type battery like you’d find in small toys or traditional watches. Clearing CMOS, in this case, involves popping the battery out and then putting it back in.

If your computer is more than 5 years old this might be a great time to replace the battery. Eventually, these batteries do die and it’s better to replace them on your own terms than have to deal with it later when you are in the middle of an important project.

Clear CMOS Using This Motherboard Jumper

Yet another way to clear the CMOS is to short the_CLEAR CMOS_ jumper on your motherboard, assuming your motherboard has one. Most desktop motherboards_will_ have a jumper like this but most laptops and tablets_will not_ .

Make sure your computer is unplugged and then open it up. Look around your motherboard’s surface for a jumper (as shown in the picture) with theCLEAR CMOS label, which will be located_on the motherboard_ and near the jumper.

These jumpers are often located near the BIOS chip itself or next to the CMOS battery. Some other names by which you might see this jumper labeled include_CLRPWD_ ,PASSWORD , or even just_CLEAR_ .

Move the little plastic jumper from the two pins it’s on over to the other pins (in a 3-pin setup where the center pin is shared) or remove the jumper entirely if this is a 2-pin setup. Any confusion here can be cleared up by checking the CMOS clearing steps outlined in your computer or motherboard manual.

Turn the computer back on and make sure that the BIOS settings have reset, or the system password is now cleared — if that’s why you were clearing CMOS.

If everything is good, turn off your computer, return the jumper to its original position, and then turn the computer back on. If you don’t do this, CMOS will clear on every restart of your computer!

Why Clear CMOS?

One reason to reset CMOS is to help troubleshoot or solve certain computer problems or hardware compatibility issues. Many times, a simple BIOS reset is all you need to get a seemingly dead PC back up and running.

You might also want to clear CMOS to reset a BIOS or system-level password, or if you’ve been making changes to BIOS that you suspect have now caused some kind of problem.

After Clearing CMOS

After clearing the CMOS you may need to access the BIOS setup utility and reconfigure some of your hardware settings. While the default settings for most modern motherboards will usually work just fine, if you’ve made changes yourself, like those related tooverclocking , you’ll have to make those changes again after resetting BIOS.

What Settings Are in the BIOS?

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