How to Reset RAM to 0 When the CMOS Battery Has Failed

Computer RAM comes in SIMMS, DIMMS and RIMMS.

You can replace a defective CMOS battery with a new one and reset the hardware settings so that RAM and other components are recognized by the computer's basic input/output system. If you power on your computer and hear a series of beeps and nothing happens, or if your computer won't boot at all, it might be due to a defective CMOS battery. The battery provides power to the BIOS memory so that it retains the settings for your specific computer. The battery must be replaced so that the BIOS can be reset and the RAM recognized afresh.

Things You'll Need

• Anti-static wrist strap
• Small flat-head screw driver
• Cross-head screw driver

Instructions

1. Power off your computer and unplug the power cord. If it's a laptop, remove the battery. Attach the anti-static wrist strap to your wrist and clip the end of the wire to a piece of grounded metal. The case of the computer works well for a ground.

2. Remove the cover on the computer according to the manufacturer's specifications. Set aside the cover and any hardware. Locate the CMOS battery on the motherboard. It is typically a shiny, coin-type battery. Use your fingernails or the small flat-head screwdriver to gently pry up the battery. Note the size and voltage of the battery and get a new one to replace it.

3. Let the computer sit without the CMOS battery for at least two hours to allow any capacitors to fully discharge. Remove all of the RAM. Typically you will gently pry the clips off of the sides of the RAM and slide it out. However, some laptops also have a rotation element. Consult your manual for more details.

4. Insert the new CMOS battery. The writing should face up and the blank side should be down. Press it firmly into place so the metal around it grips it tightly. Replace the power cord and press the power button on your computer. It will not boot because there is no RAM available.

5. Remove the power cord and wait one minute or until the light on the motherboard goes out. Replace one stick of RAM. Replace the power cord and power on the machine. Press the button to enter the "Setup" system. This is the BIOS on your computer where you can adjust the hardware settings. Common keys are "Del" or "F2" but it will display on the screen just after you power it on.

6. Find the option to reset the BIOS settings. It may be labeled as a "Default Settings" or "Standard Settings" depending on your BIOS manufacturer. It will restore all of the standard settings for your BIOS. When you're done, save and exit the BIOS. Power down your computer and unplug the power cord.

7. Replace the remaining RAM after the light on the motherboard goes out or one minute has passed. Replace the cover and the hardware holding it in place. Replace the power cord -- and battery, if any -- and power up the system. It will recognize the RAM anew as if starting from zero.

Tips & Warnings

• Some motherboards use a wired CMOS, so remove the wire and the battery.

• If the CMOS battery is hard wired to the BIOS chip, you can't replace it yourself. Consult your manufacturer for help.

References

• Computer Hope: How can I reset CMOS / BIOS settings?
• PC Guide: Computer CMOS Settings
• Computer Hope: How to replace the CMOS battery