November 2016

When a CMOS Checksum error occurs during system startup, it could mean that the system has been restored to default factory settings. The CMOS contains data related to BIOS and may have been reinitialized. It may also be possible to fix the problem by reinitialising BIOS. The problem could also occur due to the depletion of the CMOS battery. If the user cannot locate the pin battery, the help of a computer technician should be taken to prevent damage to the hardware or motherboard. The CMOS checksum error - defaults loaded should be solved after changing the CMOS battery.


When starting your PC, the following error message is displayed:

CMOS wrong      
CMOS Checksum Bad      
CMOS checksum error defaults loaded      
Warning! CPU has been changed please re-enter cpu settings in the cmos setup and remember to save before quit!      

You are prompted to:
Press F1 to resume    
Press F2 to load default values and continue

This is due to the fact that the CMOS, which contains data related to the BIOS, has been reinitialized and that your PC has been reset to factory settings.


  • Reinitializing the BIOS
  • Change BIOS battery
    • If the problem persists this may be due to the fact that the battery powering the CMOS (when the computer is shut down it allows the CMOS to store information), is depleted.
    • The CMOS battery is a small pin found on the motherboard; you can refer to the manual provided with your motherboard to change it or have the nearby computer technician change it for you if you don't want to risk any damage.
    • More information with: Replacing the battery of your motherboard (CMOS battery)

Related :

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