Fixing the "CMOS Checksum is Invalid" Error on Startup

The "CMOS Checksum is Invalid" error message that appears during startup generally indicates issues with BIOS settings or the CMOS memory. This error can disrupt the normal boot process. Let’s explore what this means, its causes, and how to fix it.

What Does "CMOS Checksum is Invalid" Mean?

The CMOS chip stores BIOS settings and system time, ensuring that basic settings are retained even when the computer is powered off. A checksum error occurs if BIOS detects that the values stored in CMOS have been altered or corrupted, which could suggest configuration or hardware issues.

Main Causes of the CMOS Checksum Error

  • Drained CMOS battery: The CMOS settings are backed up by a battery, and if it loses power, data may be lost, leading to a checksum error.
  • Reset BIOS settings: BIOS settings can sometimes be reset after an update or if the system configuration has been changed, triggering an error.
  • Hardware issues with the motherboard: Faults in the motherboard or related components could also cause this error.
  • Malware or viruses: Some viruses are known to alter CMOS and BIOS settings.

How to Fix the "CMOS Checksum is Invalid" Error

  1. Replace the CMOS battery: Usually, a CR2032 battery powers CMOS. Power down the computer, locate the battery on the motherboard, and replace it. Then, enter BIOS to set the system time and date again.
  2. Reset BIOS settings: During startup, enter the BIOS (typically by pressing DEL, F2, or F10) and select “Load Setup Defaults” (or a similar option based on your system). Save the changes and restart.
  3. Update BIOS: Updating BIOS can sometimes resolve checksum issues. Download the latest BIOS version from the motherboard manufacturer’s website and follow the instructions to install it.
  4. Scan for malware: Run a trusted antivirus software to rule out the possibility of malware tampering with your system.