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How to clear CMOS via battery removal

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Category: Technical Support
Forum Name: Intel Motherboards
Forum Description: Question about ASRock Intel Motherboards
Printed Date: 26 May 2024 at 4:07pm
Software Version: Web Wiz Forums 12.04 -

Topic: How to clear CMOS via battery removal
Posted By: Xaltar
Subject: How to clear CMOS via battery removal
Date Posted: 12 Aug 2015 at 9:08pm
I have found myself giving the same advice in many threads so I have decided to place the information here. 

The clear CMOS jumper and reset factory defaults are not always effective in solving BIOS value corruption and so the only other recourse is to remove the CMOS battery. Many people are aware of this method but fairly often it is not done correctly and hence does not resolve the issue. Below I will outline a foolproof method to achieve a full CMOS clear.

1. Disconnect the system's power from the wall
2. Press and hold the power button for 10 seconds to be sure residual power is discharged
3. Place the "Clear CMOS" jumper in the clear position
4. Remove the CMOS battery
5. Leave the system in this state for 4 hours. 10 minutes is enough in most cases but if that yields no result then to be absolutely certain CMOS is clear I recommend 4 hours.
6. Place the "Clear CMOS" jumper back in its original position
7. Replace the CMOS battery
8. Power on the system

This method should effectively rule out BIOS value corruption as a culprit during troubleshooting. 

BIOS value corruption = corrupted settings in the BIOS
BIOS corruption = Corrupt BIOS/UEFI firmware due to a bad flash

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