Tip & How-To about Computers & Internet
CMOS Checksum Bad or CMOS Date/Time Not Set
This issue is caused when the CMOS values are incorrect. This issue can occur because of any of the below possibilities.
* Bad or old CMOS battery.
* BIOS update.
1. Disconnecting power from computer without shutting down computer.
2. Attempt to reboot the computer. If error still occurs after rebooting the computer enter CMOS setup and check all values, this includes verifying the time and date are correct. Once everything has been verified and/or changed make sure you save and exit CMOS setup.
3. If you have a Phoenix BIOS and have an option for 'Reset Configuration Data', set this value to 'Yes' and save and exit the CMOS.
4. If the computer was had the power disconnected while it was still running it is possible this could cause the CMOS to become corrupt. Ensure that the computer is ready to be shut off before turning off the computer. If you have a laptop computer ensure that the battery is charged before disconnecting the power connection.
5. If the CMOS values have become corrupted entering the values in CMOS setup and saving and exiting CMOS should resolve your issues.
Note: If this issue continues to occur after you turn off your computer off it is possible that the CMOS battery may be failing or already bad. Before considering replacing the CMOS battery try leaving your computer on for several days.
If you performed workaround 1 and the error occurs again after a complete power down (i..e. removing the power cord), the CMOS battery is likely bad. Most systems use a small coin style lithium battery. These often last 3-6 years, but at some point run out of juice and need to be replaced. For desktops, your system manual or motherboard manual should specify the type of battery and location on the motherboard. For laptops, it is often very difficult to access and may require a professional to replace it. To replace the battery on a desktop system:
1. Turn off the system and remove the power plug.
2. Remove the case or side panel to access the motherboard.
3. Look for a round silver coin cell, typically in a black holder.
4. Remove the battery while noting which way the battery is located. You may need a small flat screwdriver to release the side clip.
5. Install the replacement battery with the same battery type, being careful to insert it in the same direction as the removed battery (or using the polarity marked on the holder or manual).
6. Reassemble the case and power.
7. Turn on the power. You will get the CMOS Checksum Bad error once more, but it should be the last time. Go into the BIOS setup and set the date and time, and any other options you prefer.
Posted by Archie... on
Reboot the computer.
If error still occurs after rebooting the computer enter CMOS setup and check all values, this includes verifying the time and date are correct.
During the boot process you will see on the screen a certain key to press to enter setup
Press and hold that key during the boot up process to enter BIOS you can load failsafe defaults or load optimized defaults ,press escape then press f10 to save to cmos to restart
You will also need to set the time and date
In the main or system setup screen you should be able to see the date and time Using your arrow keys navigate to the date and change the date. Once highlighted on the month, day, or year, press your arrow keys or your page up / page down keys to change the date.
Once everything has been verified and changed make sure you save and exit CMOS setup.
If everything appears to be correct and the issue persists try resetting the CMOS values to the defaults or Reset Configuration Data.
If this issue continues to occur after you turn off your computer off it is possible that the CMOS battery may be failing or already bad. Before considering replacing the CMOS battery try leaving your computer on for several days.
If a BIOS update has been run on the computer the values stored in CMOS may have been reset. Enter CMOS setup re-enter all values and then save and exit CMOS setup.
If you're unable to enter the CMOS setup or after running a BIOS update your computer no longer keeps its values the incorrect BIOS update may have been installed for your computer or the version downloaded may be corrupt. We suggest trying to update the BIOS again or reverting back to an earlier version.
Hope it helps
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