How to fix Windows CMOS checksum error (resolved)

If you want to know how to fix the CMOS checksum error, you should read this post. It will show you the main causes of this error. Besides, you will get useful solutions to fix this error. For now, you can get these viable methods from the Techquack website.

The CMOS checksum error is essentially a conflict between the CMOS and the BIOS that occurs when the PC starts up. When the computer shuts down, the CMOS writes a number that should match the number that the BIOS generates when the computer reboots.

If the two values do not match, the PC may return a CMOS checksum error. This is an error detection mechanism called a “checksum,” also known as a redundancy check to detect errors in the data.


How CMOS and BIOS work

How CMOS and BIOS work

A BIOS (Basic Input/Output System) is a set of parameters/commands on a CMOS chip that resides on a computer motherboard.

While the operating system controls the software running on the computer, the BIOS is more like the firmware that checks the memory, processor, and peripheral hardware components of the computer so that the operating system can boot properly.

The BIOS synchronizes important system data, such as time and date, with the CMOS. It works independently of the operating system you use on your PC and manages the relationships between all of the PC’s hardware components.

But in fact, the operating system can’t run without the BIOS, because that’s where all the operating system drivers are loaded. The BIOS itself is stored in CMOS (Complementary Metal Oxide Semiconductor). Therefore, the CMOS contains all the BIOS settings.

When the BIOS fails, booting the computer becomes problematic because it cannot match the BIOS settings before shutting down the computer and while booting.


What is the cause of a CMOS checksum error in Windows?

What is the cause of a CMOS checksum error in Windows?

Improper system shutdown: This is one of the most common causes of CMOS errors; improper system shutdown can corrupt BIOS values. A sudden power failure while using your computer can also affect the CMOS and cause this error message.

After updating the BIOS: Sometimes when a user updates the system BIOS, the values stored in the CMOS may be reset. Therefore, it is recommended to reboot the CMOS and reconfigure all values. Then save and exit the CMOS configuration.

Low Battery: If the battery required by CMOS to maintain the BSOD settings while the computer is turned off is low, it will cause a checksum error.

Damaged or outdated BIOS: To stay in sync with the operating system and hardware components, the BIOS must be updated. Sometimes the cause of the error becomes more sinister, as viruses discreetly change the checksum value. In this case, a CMOS checksum error occurs.

Damaged motherboard: If your computer’s motherboard is physically damaged, this can lead to this CMOS error.

How to fix a CMOS checksum error in Windows 10?

How to fix a CMOS checksum error in Windows 10?

Replace the CMOS battery

One of the main causes of this problem is the CMOS battery. If the battery is older than a few years, it can no longer supply enough voltage to the CMOS, and this problem is bound to occur. This is a clear sign that it’s time to replace the battery with a new one. These batteries are inexpensive and you can’t start your computer without them, so be sure to follow the instructions below!

1.) Open the computer case and find the CMOS battery that is connected to the computer’s motherboard. If you cannot find the CMOS battery pack, refer to your motherboard or computer documentation. You can also consult the Internet or ask the manufacturer of your computer for help.

Note: Some computers may require you to disconnect cables, remove disks, or remove other parts of the computer to physically access the CMOS battery.

2.) If your computer uses a coin cell battery, it is relatively easy to remove. Grasp the edge of the battery with your fingers and pull it up out of the slot in which it is inserted. Some motherboards have a clip that holds the battery in place, and you may have to lift it to remove the battery.

3.) Let it out for 10 minutes, take another one, insert it in the same way, and try to start the computer. Check for a CMOS checksum error!

Resetting the BIOS to default settings

Another major cause of this problem is incorrect BIOS settings. BIOS settings don’t get corrupted too often, and it’s always a problem when they do. It could be caused by an incorrect BIOS update or even a malware program. Either way, if you can access the BIOS, a default reset should definitely fix the problem!

  1. Turn the computer on and try to access the BIOS settings by pressing the BIOS button when the system boots. The BIOS button usually appears on the boot screen and says, “Press ___ to enter the configuration” or something similar. But there are other keys as well. The usual BIOS keys are F1, F2, Del, etc.
  2. The default values boot option can be in two different places on the BIOS screen, depending on the BIOS version of the Dell computer.
  3. If you see the Restore Settings button at the bottom of the main BIOS settings screen next to the Exit button, click it and make sure you have selected the default BIOS settings before clicking OK. Click Exit and your computer will reboot.
  4. If this button is missing, you can access the Exit tab on the BIOS home screen by pressing the right arrow key on your keyboard until you reach it. Click the down arrow key until you reach the Restore Defaults (or Load Defaults) option, then press Enter.
  5. Press Enter again when you are prompted to Load Defaults, and wait for your computer to start up. Make sure that the problem is resolved.
BIOS Repair (Intel motherboards)

On Intel desktops, there is a problem where a certain version of BIOS will just start displaying the problem after a while. The only way to solve this problem is to perform a BIOS recovery by installing the latest version using a bootable USB stick. Do the following steps only if you have an Intel desktop board!

  1. Visit their website and find the latest BIOS version available for your installation. Be sure to enter the appropriate installation information to find the file you need. Be sure to download it to your computer.
  2. Make sure it is formatted to FAT32 before copying the file to your USB device. Open the “Libraries” entry on your PC or open any folder on your computer and click on the “This PC” option on the left menu. If you are using an older version of Windows (Windows 7 and above), just open My Computer on your desktop.
  3. Right-click on the USB drive you want to format and select Format… from the pop-up menu that appears.
  4. A small window called Format will open. Be sure to click on the menu under File System and select the FAT32 file system if it is not already selected. Click Format and wait for the process to complete.
  5. Be sure to copy the file to the USB device. The file must be in the root folder (the folder that opens when you double-click on the USB device in this PC).
  6. Connect the USB device to the target PC’s USB port, turn off the PC and unplug the power cord. Open the case and remove the BIOS setup jumper. Its position is shown below.
  7. Turn on the computer and wait a few minutes to complete the update. The computer will shut down automatically or ask you to turn it off manually. Either way, remove the USB device and put the BIOS setup jumper back in place (above – picture to the right).
  8. Close the computer case and restart the computer to make sure the CMOS checksum error still appears on the computer!
Reboot the computer.

A normal restart usually generates a new checksum and clears the error. An error that persists after a normal restart requires a little more work.

Contact a technician or computer repair technician.

If all of the above measures fail, the problem may be property damage. Before buying a new motherboard or reworking the device, make sure it has been checked by a specialist.


Frequently Asked Questions

  1. Reboot the computer. A normal restart usually generates a new checksum and fixes the error.
  2. Download and flash the BIOS update. Download the update from the motherboard manufacturer's website.
  3. Reset the BIOS.
  4. Replace the CMOS stack.
  5. Consult a technician or computer repair specialist.

A CMOS checksum error is an error that occurs when incorrect CMOS values are detected. CMOS memory usually stores a certain value to protect the BIOS software. Each time the computer starts up, this value, which is a number, is compared to the value stored in the CMOS memory.

The most common cause of a checksum error at startup is a defective battery that does not provide sufficient power to the motherboard when the computer is turned off. However, motherboard failures and viruses can also contribute to checksum errors.

  1. Turn off the computer.
  2. Unplug the power cord to make sure your computer is not getting power.
  3. Make sure that you are logged into the system.
  4. Locate the motherboard battery.
  5. Remove it.
  6. Wait five to 10 minutes.
  7. Replace the battery.
  8. Turn on the computer.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog,, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.