How to Clear CMOS to Fix a PC That Won’t Boot (2026 Guide)

When your PC refuses to boot and you have already tried the usual fixes, learning how to clear CMOS to fix a PC that won’t boot can be the breakthrough step that gets your system running again. I have used this exact procedure on dozens of motherboards over the years, from budget boards to high-end gaming rigs. It is one of the most effective troubleshooting techniques when BIOS settings go wrong and your system goes silent.

Clearing CMOS resets your motherboard’s firmware settings back to factory defaults. This wipes out any corrupted overclock profiles, misconfigured boot orders, or scrambled BIOS data that may be blocking startup. The process is safe, does not touch your files or operating system, and takes about 10 minutes from start to finish.

In this guide, I will walk you through three proven methods to clear CMOS, explain exactly what settings you will lose (and what stays safe), and show you how to confirm the reset actually worked. I will also cover what to do if clearing CMOS does not fix your boot problem, because that is a scenario most guides completely ignore.

What Is CMOS and What Does It Store?

CMOS stands for Complementary Metal-Oxide-Semiconductor, which is the type of memory chip on your motherboard that stores your BIOS settings. Think of it as a tiny notepad where your motherboard writes down every configuration choice you make in the BIOS setup screen. This chip is powered by a small coin-cell battery (usually a CR2032) so it retains your settings even when the PC is unplugged.

The CMOS chip stores several pieces of information that your computer needs before it can load Windows. These include the system date and time, boot device priority, CPU and RAM voltage and frequency settings, fan speed curves, integrated peripheral toggles (like enabling or disabling USB ports), and any BIOS administrator password you may have set.

When you clear CMOS, you are essentially erasing that notepad. Your motherboard reads the now-empty memory, realizes there is no saved configuration, and loads safe factory defaults instead. This is why clearing CMOS is so effective for boot problems: it removes any setting that might be causing a conflict and gives you a clean starting point.

CMOS is different from your hard drive or SSD. Your files, installed programs, browser history, saved passwords, and operating system are all stored on your main storage drive and are completely untouched by a CMOS clear. The reset only affects motherboard-level firmware settings.

Signs Your PC Needs a CMOS Clear

Before you open your case, it helps to confirm that CMOS corruption is actually a likely culprit. Based on my experience and what users report on forums like r/buildapc and Tom’s Hardware, here are the most common symptoms that point to a CMOS issue.

Your PC powers on but produces no display output. The fans spin, the RGB lights up, but your monitor stays black or says “No Signal.” This is one of the most frequent signs that BIOS settings have become unstable, especially after an overclocking attempt or a BIOS update gone wrong.

Your system gets stuck in a boot loop. It turns on, runs for a few seconds, shuts down, and then starts back up again in an endless cycle. This often happens when the motherboard tries to apply memory timings or CPU settings that the hardware cannot handle.

You see a message on startup asking you to press a key to load default settings, or you get a “CMOS Checksum Error” message. These are your motherboard’s way of telling you that the stored settings do not match what it expects, and it needs a clean slate.

You recently installed new hardware (a new CPU, different RAM, or a fresh storage drive) and the system will not POST with the new component. The old BIOS settings may be incompatible with the new hardware, and clearing CMOS forces the motherboard to re-detect everything from scratch.

You forgot your BIOS password and cannot enter the setup utility. Clearing CMOS wipes the stored password along with all other settings, giving you access again.

Method 1: Clear CMOS Using the Jumper Pins

The jumper method is the most reliable way to clear CMOS and is supported by nearly every desktop motherboard. Every manufacturer includes a dedicated pair of pins on the board specifically for this purpose, typically labeled CLR_CMOS, CLRTC, CLEAR_CMOS, or JBAT1. I start with this method because it works consistently across brands.

Step 1: Shut down completely and unplug the power cable. Turn off your PC normally if possible. If the system will not respond, hold the power button for 10 seconds to force a shutdown. Once the system is off, physically unplug the power cable from the wall or the back of the power supply. This step is non-negotiable. Working inside a powered PC can damage your components.

Step 2: Locate the CLR_CMOS jumper on your motherboard. Open your case and look for a pair (sometimes three) of small metal pins sticking up from the board. They are usually near the CMOS battery or along the bottom edge of the motherboard. Check your motherboard manual for the exact location, since the labeling varies between ASUS (CLRTC), MSI (JBAT1), Gigabyte (CLR_CMOS), and ASRock (CLRTC). If you lost your manual, you can find a PDF version on the manufacturer’s support page by searching your motherboard model number.

Step 3: Move the jumper cap to the clear position. Most jumper pins come in a set of three with a small plastic cap covering two of them. The cap connects pins 1 and 2 in normal operation. To clear CMOS, remove the cap and place it so it connects pins 2 and 3 instead. If your board only has two pins (no cap), touch both pins simultaneously with a metal screwdriver blade for 10 seconds. This bridges the connection and triggers the reset.

Step 4: Wait 10 to 15 seconds. Hold the jumper in the clear position for at least 10 seconds to make sure the CMOS memory fully discharges. I usually count to 15 to be safe.

Step 5: Return the jumper to its original position. Move the cap back to pins 1 and 2. If you used a screwdriver on a two-pin setup, simply remove the screwdriver. Do not forget this step. If the jumper is left in the clear position, your PC may refuse to boot or will clear CMOS on every restart.

Step 6: Reconnect power and turn on your PC. Plug the power cable back in and press the power button. Your system should now boot with factory-default BIOS settings.

Method 2: Remove the CMOS Battery

If you cannot find the jumper pins or the jumper cap is missing (this happens more often than you might think, and forum users complain about losing them constantly), the battery removal method is your next best option. This method works because the CMOS chip needs continuous power from the battery to retain its settings. Remove the power source, and the settings fade away.

Step 1: Power down and unplug. Just like with the jumper method, shut down your PC completely and remove the power cable. Wait an additional 30 seconds after unplugging to let the capacitors in your power supply drain.

Step 2: Locate the CMOS battery on the motherboard. Look for a shiny silver coin-cell battery, almost always a CR2032 type. It is about the size of a nickel and sits in a circular holder on the board. It is typically near the bottom-right quadrant of the motherboard when viewed from the front of the case.

Step 3: Release the battery from its holder. Most battery holders have a small metal or plastic tab on one side. Press this tab gently with a fingernail or a non-metallic tool, and the battery will pop up at an angle. If the battery is stubborn, use a small flathead screwdriver to carefully lever it out. Be gentle so you do not snap the retention tab. On some older boards, the battery is wrapped in shrink-wrap and connected by a wire to a two-pin header. In that case, simply unplug the connector from the header.

Step 4: Wait 5 to 10 minutes. This is where patience matters. Some motherboards have additional capacitors near the CMOS chip that keep the memory alive for a short while after the battery is removed. I recommend waiting at least 5 minutes to guarantee a full reset. If you want to be absolutely certain, wait 10 minutes. Many forum users who report that CMOS clearing “didn’t work” simply did not wait long enough.

Step 5: Press and hold the power button for 10 seconds. While the battery is still out, press the power button on your case (with the power cable still unplugged). This drains any residual charge from the motherboard capacitors and ensures a thorough reset.

Step 6: Reinstall the battery and reconnect power. Place the CR2032 back into its holder with the positive side (the side with writing on it) facing up. You should feel it click into place. Reconnect the power cable and start your PC.

Method 3: Use the Clear CMOS Button

Newer motherboards, especially mid-range and high-end gaming boards from ASUS, MSI, and Gigabyte, include a dedicated Clear CMOS button. This is by far the easiest method because it requires no case opening and no battery removal. I have seen this feature save enormous amounts of time, especially for users who build inside cases with limited access to the motherboard.

Check your I/O panel first. On some boards, the Clear CMOS button is on the back of the computer, right on the motherboard I/O shield where you plug in your keyboard, mouse, and monitor. It is usually a small recessed button labeled “Clear CMOS” or “BIOS_FLR” and requires a paperclip or pen tip to press. This design prevents accidental presses.

Check onboard buttons too. Many gaming motherboards have the Clear CMOS button built directly onto the board itself, near the bottom edge or in the corner. These are larger and easier to press. Look for a button labeled “CLR_CMOS” or one with a small gear icon.

The reset procedure is simple. Shut down the PC completely but leave the power cable connected (the button needs a small amount of standby power to function). Press and hold the Clear CMOS button for 5 to 10 seconds until you see the system power cycle or hear a click. Release the button and wait for the system to restart automatically, or press the power button if it does not.

Not sure whether your board has this feature? Check the specifications page on the manufacturer’s website by searching your exact model. Look for “Clear CMOS Button” in the feature list. Alternatively, flip through the included quick-start guide that came with the motherboard.

If your board has BIOS FlashBack (a feature found on many ASUS and some MSI boards), note that this is different from a Clear CMOS button. BIOS FlashBack reflashes the entire BIOS firmware from a USB drive and should only be used if the BIOS is severely corrupted, not for a standard CMOS reset.

What to Do After Clearing CMOS

Once you have cleared CMOS and powered on your PC, there are several steps you should take to confirm the reset worked and get your system back to a usable state. This post-reset phase is where I see most users get confused, so I will walk you through it carefully.

Watch for the BIOS setup prompt. After a successful CMOS clear, most motherboards display a message on first boot saying something like “BIOS has been reset” or “Please enter Setup to configure your system.” This is your first confirmation that the reset worked. Press the designated key (usually F2, Del, or F1) to enter the BIOS setup screen.

Load optimized defaults. Even though the CMOS clear already restored factory settings, I recommend explicitly loading optimized defaults from within the BIOS. Look for an option called “Load Optimized Defaults,” “Load Setup Defaults,” or “Restore Defaults” (usually under the Exit or Save menu). This ensures the board loads the manufacturer’s recommended baseline rather than the absolute minimum fallback settings.

Check the date and time. If the date and time have reverted to an old default (often something like January 1, 2010, or the board’s manufacturing date), this confirms the CMOS was fully cleared. You can set the correct date manually or let Windows sync it once you are back in the operating system.

Reconfigure your essential settings. Review the following categories and adjust as needed for your system: boot device order (make sure your main SSD or hard drive is first), SATA mode (AHCI vs RAID, if applicable), XMP or DOCP profile for your RAM (to run it at rated speeds), and fan curves if you had customized them. Skip any overclocking for now. Get the system booting stably with defaults first.

Save and exit. Press F10 (on most boards) to save all changes and reboot. Your PC should now boot into Windows normally. If it does, your CMOS clear was successful.

How to verify the reset worked: Your system boots to the BIOS setup screen on first power-on, the date and time show a default value, any BIOS password you had set is gone, and any custom overclock profiles are no longer listed. If all four of these are true, the CMOS reset was complete and successful.

What If Clearing CMOS Doesn’t Fix the Boot Problem?

Here is the section most guides skip entirely. If you cleared CMOS and your PC still will not boot, the problem is not BIOS settings. You need to escalate your troubleshooting to other hardware components. Based on patterns I have seen across tech support forums, here is the escalation path I recommend.

Recheck your power supply. A failing or underpowered PSU can mimic BIOS corruption symptoms. Try a different power cable, test the wall outlet with another device, and if possible, try a known-good power supply. Listen for the PSU fan when you power on. If there is no fan spin and no lights at all, the PSU may be dead.

Test your RAM. Remove all RAM sticks and test each one individually in the first slot (usually slot A2 or DIMM_A2, depending on your board). If the system boots with one stick but not others, you have a faulty module. If it still does not boot with any single stick, the problem may be the motherboard’s memory channel or the CPU’s memory controller.

Reseat your GPU and storage drives. Remove your graphics card and plug it back in firmly. Do the same with your SSDs and hard drives. A loose connection after a case cleaning or a bump can prevent booting entirely.

Inspect the CPU. If you recently installed a new CPU, check for bent pins (on Intel boards with LGA sockets, check the socket itself; on AMD AM4 boards, check the CPU). Even one bent pin can prevent POST. Reseat the CPU carefully with proper alignment.

Try a bare-minimum boot. Strip the system down to just the CPU, one RAM stick, the boot drive, and integrated graphics (remove the dedicated GPU if your CPU has integrated graphics). If it boots, add components back one at a time to identify the problematic part.

When to seek professional help: If you have tried all of the above and the system still shows no signs of life, you likely have a dead motherboard or CPU. At that point, a professional repair shop or RMA through the manufacturer warranty is your best path forward. Do not keep repeatedly clearing CMOS hoping for a different result. As one frustrated Reddit user put it, “I cleared CMOS six times before realizing my motherboard was actually dead.”

What You Lose and What You Keep When Clearing CMOS

This is the question I get asked most often: will clearing CMOS destroy my data? The short answer is no. Your files, photos, games, documents, and operating system are completely safe because they live on your storage drive, not in CMOS memory. Here is exactly what changes and what stays the same.

Settings that will be reset to defaults: Boot device order, CPU multiplier and voltage settings, RAM frequency and timings (XMP/DOCP profiles turn off), fan speed curves, RGB lighting configurations, integrated audio and network toggles, BIOS administrator password, system date and time, and any saved overclock profiles.

Data and settings that are completely preserved: Everything on your hard drive or SSD, your Windows installation and product key, all installed programs and applications, browser data and saved passwords, game saves and progress, personal files of every type, network Wi-Fi passwords (these are stored in Windows, not BIOS), and peripheral settings stored in device firmware.

When you should NOT clear CMOS: If your system is running fine and you are just curious, do not bother. There is no benefit to clearing CMOS on a healthy system. Also, if your system boots but runs slightly differently than you prefer, you can fix individual settings in the BIOS without a full reset. Clearing CMOS should be a targeted fix for a specific problem, not a routine maintenance task.

Frequently Asked Questions About Clearing CMOS

Wrapping Up

Knowing how to clear CMOS to fix a PC that won’t boot is a skill every PC owner should have in their troubleshooting toolkit. Whether you use the jumper pins, the battery removal method, or the dedicated Clear CMOS button, the goal is the same: wipe corrupted BIOS settings and give your motherboard a clean starting point.

The process is safe, does not touch your personal data, and resolves a surprising number of boot problems. Start with Method 1 (the jumper), move to Method 2 (battery removal) if the jumper is not accessible, and use Method 3 (the button) if your modern motherboard supports it. After the reset, load optimized defaults, reconfigure your boot order and RAM profile, and you should be back in Windows within minutes.

If clearing CMOS does not fix the issue, shift your focus to other hardware components like the power supply, RAM, and CPU connections. And if your system boots fine after a CMOS clear but reverts to failing on the next restart, replace that CR2032 battery. It costs less than a cup of coffee and might save you hours of frustration.