How to Reset CMOS and Replace the Motherboard Battery

What CMOS and the motherboard battery do

CMOS is the small memory area on the motherboard that stores firmware settings: the system clock, boot order, memory timing profiles, integrated device states, fan curves, and security options. A coin-cell battery on the board keeps that memory powered after the PC is unplugged, which is why the settings survive from one boot to the next. The battery does not run the CPU or memory during normal operation; it only preserves the stored configuration.

Resetting CMOS returns those firmware settings to the board's factory defaults. It does not erase your drives, remove Windows, or change the operating system. Your personal files and installed programs stay exactly where they are. The reset acts on motherboard-level configuration, so treat it as a board procedure rather than a software recovery tool. To understand where these settings live, see the BIOS and UEFI guide.

When to reset CMOS

Reset CMOS when the board is stuck with a configuration it cannot start from. The most common reason is a failed boot after you changed memory settings, CPU options, or other firmware values. Clearing the settings gives the board a fresh starting point. Many boards also use the reset to clear a forgotten firmware password.

Check simpler causes before you reach for the CMOS reset. A loose power cable, poorly seated memory, or a display connected to the wrong port can cause the same blank screen. The motherboard debug LED guide explains how to read the board's status LEDs and identify the failing component. Use the reset when the board itself is holding bad settings, not when the issue is a loose connection.

• The PC powers on but shows no display after firmware settings were changed.
• Memory training fails repeatedly after you installed new RAM or enabled a high-frequency profile.
• You changed CPU-related options and the system will not start.
• The board asks for a firmware password you no longer know.
• A CPU or memory upgrade leaves the board unstable.

How to clear CMOS with a jumper or button

Motherboards clear CMOS in different ways depending on the chipset and the board maker. The board manual is the final authority, because Intel's desktop chipset lineup includes mainstream, enthusiast, gaming, content creation, and business models with different layouts. On many boards the clear point is a header labeled CLR_CMOS, CLRTC, CMOS Reset, or something similar near the battery, the board edge, or the rear I/O panel. Newer boards often add a rear-panel button that is easier to reach.

After clearing, power on and enter the firmware setup using the key shown on the startup screen. The board will load defaults or ask you to set the date and time. If the system starts, go back into the firmware and confirm that boot order, memory, and security options are set the way you want.

• Turn off the PC and unplug the power supply. Press the case power button afterward to drain any stored charge. The cables you see inside are covered in the motherboard power connectors guide.
• Find the clear header or button. If the board has a rear-panel clear CMOS button, you usually press and hold it while the power is off, but confirm the exact step in the manual.
• For a jumper header, use the jumper cap or a metal tool to briefly short the appropriate pins, then restore the cap to its normal position. Follow the time given in the manual.
• On boards with a button, press it as described in the manual and wait before powering the system on.
• Restore the jumper to its normal position before plugging the PC back in. A cap left in the clear position can keep the board in a reset state.

How to replace the motherboard battery

Many motherboards use a flat CR2032 coin-cell battery in a small metal holder. It looks like a watch battery and is usually near the chipset, the PCIe slots, or the edge of the board. If the system clock loses time whenever the PC is unplugged, or the board forgets settings while off, a weak battery is a likely cause.

Removing the battery is not the same as pressing a clear button. Cutting battery power clears CMOS on many boards, but some boards hold their settings long enough to survive a quick battery swap. If you need a guaranteed reset, use the jumper or button when the board has one, then replace the battery if the clock still does not keep time.

• Unplug the power supply and remove the side panel. If the battery is under a large cooler or drive cage, remove the board from the case for better access.
• Locate the battery and note its orientation. The plus symbol on the battery usually faces up, but some holders are reversed.
• Press the retaining clip with a non-metal tool or your fingertip and slide the battery out. Avoid bending the holder or prying against the circuit board.
• Insert the replacement battery with the same orientation and make sure the clip holds it firmly.
• Reconnect power and start the PC. If the board was unplugged for a while, the CMOS values may already be cleared, and you will likely need to set the date and time before Windows loads.

What to do after resetting CMOS

A CMOS reset restores default firmware values, so any feature you enabled in the firmware needs to be set again. The date and time usually come first. Then re-enable memory performance profiles such as XMP or EXPO if you want the memory to run at its rated speed; the XMP and EXPO memory overclocking guide explains the difference between the two.

On a Windows 11 PC, also verify firmware security settings. Microsoft lists UEFI with Secure Boot capability and TPM 2.0 among the minimum system requirements, and a reset can return those options to disabled or default. If you use BitLocker or other security features, re-enable Secure Boot and TPM before relying on them.

Firmware settings also control many I/O and network options. The USB4 architecture is designed to share a single high-speed link between data and display protocols, and Wi-Fi 7 products operate across the 2.4, 5, and 6 GHz bands. After a reset, confirm that USB controllers, the network adapter, and the boot drive are set to the configuration you use. These settings vary by board, so the manual and the how to read motherboard specs guide are useful references.

When resetting CMOS is not enough

Clearing CMOS cannot repair a corrupted firmware image. If the board tries to start but stays at a blank screen even with defaults loaded, the firmware itself may need to be updated through a USB flashback port. That procedure is separate from a CMOS reset; the BIOS flashback guide explains when to use it.

A reset also will not fix damaged hardware. If the board has debug LEDs, check which component they point to before assuming the CMOS settings are at fault. On an older board with a failing power delivery circuit or a damaged socket, no amount of clearing will make the system stable. In that case, compare current boards such as the best budget motherboards and the best gaming motherboards guides when you plan to replace the board.

What to pick for your use

Questions

Does clearing CMOS delete files or Windows?

No. CMOS stores motherboard firmware settings, not personal data. Resetting CMOS returns those settings to defaults. Drives, files, and installed operating systems are untouched.

Do I have to remove the battery to clear CMOS?

No. On most boards, a dedicated clear button or jumper is the cleaner method. Removing the battery can clear CMOS too, but the board manual may ask you to wait before reinstalling, and some boards survive a quick battery swap without clearing.

How long should I leave the battery out?

Follow the board manual. Some boards clear the moment battery power is removed, while others need a short pause before you reinstall the battery. If the settings survive, use the clear jumper or button instead.

What settings do I have to redo after resetting CMOS?

The firmware usually returns to defaults, so check the system clock, boot drive order, memory profiles, fan curves, Secure Boot and TPM, USB, and network settings. Re-enable only the settings you actually use.

Why would the battery need replacement?

If the system clock resets every time the PC is unplugged, or the board loses stored settings while powered off, the coin-cell battery is likely weak. Replacing it restores backup power for the CMOS memory.

Will clearing CMOS damage my CPU or memory?

No. CMOS holds firmware settings, not the silicon itself. A reset returns the saved settings to defaults and does not change the processor or memory hardware. On Intel desktop Core Ultra processors, suffixes such as K, F, KF, and T describe features like unlocked operation or discrete graphics needs, and those are unaffected by a CMOS reset.

Can resetting CMOS fix a no-POST problem?

It can, if the no-POST state was caused by bad firmware settings such as an unstable memory profile or CPU option. It will not fix a failed power supply, a damaged component, or a short circuit. Check the debug LEDs and the power connections first.