Pay for your PC in installments (up to 12 payments)Clear CMOS : what is it really for?
The Clear CMOS operation is a simple procedure that lets you reset the motherboard’s BIOS or UEFI.
In practice, it restores the BIOS settings to their original configuration, just like when the PC leaves the factory.
On the internet and in Google searches, the question “Clear CMOS—what is it?” comes up extremely often, because it’s one of the first solutions to try when a PC won’t boot.
What is CMOS?
The CMOS (Complementary Metal-Oxide Semiconductor) is a small memory found on the motherboard.
Its role is to store the BIOS settings thanks to the motherboard battery.
When you do a Clear CMOS, you simply erase these settings to return to the default configuration.
When should you do a Clear CMOS?
1. After a overclock gone wrong
This is very common after:
- a overclock CPU that’s too aggressive
- an unstable RAM XMP / EXPO profile
- a poorly configured undervolt
2. If the PC no longer boots
A Clear CMOS can resolve issues such as:
- black screen on startup
- PC powers on but with no display
- boot loops
3. After changing components
When you replace:
- the processor
- the RAM
- the graphics card
4. After a BIOS update
In some cases, manufacturers recommend a Clear CMOS after a BIOS update, to avoid conflicts with the previous settings.
How do you do a Clear CMOS?
Method 1: the Clear CMOS button
Some motherboards have a dedicated Clear CMOS button, often located on the back of the motherboard or directly on the PCB.
You just need to fully shut down the PC, unplug the power supply, and press the Clear CMOS button. The BIOS configuration will then be reset.
Method 2: the Clear CMOS jumper
Most motherboards have a Clear CMOS jumper.
You need to switch off the PC and cut the power supply. Locate the CLR_CMOS or JBAT1 pins on the motherboard, short the two pins together for a few seconds. Then turn the PC back on.
Method 3: remove the motherboard battery
You need to switch off the PC, unplug the power supply, remove the motherboard battery, wait about 30 seconds to 1 minute and finally reinsert the battery.
On restart, the BIOS will be reset.
Is it dangerous to do a Clear CMOS?
No, Clear CMOS is completely safe for the hardware.
It doesn’t remove Windows, files, games, or the SSD data
The only thing that gets reset is the BIOS configuration.
Mistakes to avoid
Even if the procedure is simple, you should avoid a few mistakes.
Never do a Clear CMOS with the PC turned on.
Always disconnect the power supply before any procedure.
And above all, avoid changing too many BIOS settings if you don’t know exactly what you’re doing.
Clear CMOS: does it solve all problems?
No. Clear CMOS can fix a BIOS issue, an unstable setting, or a configuration bug, but it won’t repair a faulty RAM module, a power supply that’s too weak, or a damaged motherboard.
It’s simply a very useful diagnostic step.
Why pre-built PCs often avoid this issue
On a built and tested gaming PC, the BIOS settings have usually already been validated.
The RAM profiles are configured and the components are tested together, which limits boot problems.
That’s one of the reasons why many gamers today prefer a reliable pre-built gaming PC, rather than having to manage all the technical steps themselves.
Clear CMOS FAQ
Does Clear CMOS remove Windows?
No. Clear CMOS only affects the motherboard’s BIOS.
Windows, games and files remain intact.
How long should you remove the CMOS battery for?
In general, 30 seconds to 1 minute is enough to reset the CMOS memory.
Do you need to do a Clear CMOS after a RAM upgrade?
It’s not mandatory, but it can help if the PC won’t boot after installing new memory modules.
Is Clear CMOS useful after a failed overclock?
Yes — it’s even the most common solution for getting a PC back up and running if it won’t start again after an unstable BIOS setting.
Do all motherboards have a Clear CMOS button?
No. High-end motherboards often have one, but on simpler models you need to use the jumper or remove the battery.
