CMOS Checksum Error

  the-george 21:58 23 Aug 2009

Been on holiday, came back and PC would not start- dead - no lights. Whipped back off and afterf removing power plug from motherboard and then replacing it I got moving again. However, when I start up I get a checksum error and have to press f1 to start on default values. After this everything runs fine except the clock goes back to 2001.

Could the cmos battery be faulty? Don't think it would cause PC to be totally dead - would it?

  baldydave 22:11 23 Aug 2009

Sounds like a standard flat/dead CMOS battery normally a CR2032
click here

  ambra4 22:21 23 Aug 2009

“CMOS checksum Error: Defaults loaded”

A checksum error shows that boot up settings which were previously set have been changed.

This usually happens when the battery looses its charge and thus fail to retain the CMOS settings.

This can also be caused by a power surge

Bad CMOS memory chip.

Mainboard is shorting on the case somewhere.

Something electromagnetic is effecting the CMOS memory.

A poorly shielded fan or other magnetic source is wiping out the CMOS memory periodically.

You don’t have like a refridgerator magnet on the side of the case do you?

Temperature if for some reason your mainboard has a hot-spot, excessive temperatures for the CMOS chip can cause it’s contents to scramble.

Unstable power if one of your voltage rails from the PSU is bad, it can wipe CMOS memory contents.

BIOS virus. Some virii attack the BIOS/CMOS memory space.

Common Solutions to clear this error:

Unplug the power cable wait 10 min then restart the computer

If the error persist, replace the CMOS battery

Enter the values back into CMOS or reset values to default

  the-george 15:22 24 Aug 2009

As this PC has been in use for several years I do not think it is a short, poorly shielded fan etc.

Apart from the occasional freeze - usually when using internet - There have been no real prior problems to indicate over heating or such.

So, will try a new CMOS battery and hope that solves the problem of the Checksum error.

Am using with side of case off at moment as I still have to 'wiggle' the wires to get power up. Do not think this is battery, though may be related in some way.

  the-george 15:25 24 Aug 2009

p.s.I use Avast antivirus which is up to date so this should eliminate a virus as a cause???

  lofty29 15:30 24 Aug 2009

Sounds like iffy power supply/connector prblem, be careful about sticking your hands in the case when power is on, you could get a belt also fry your motherboard.

  woodchip 15:36 24 Aug 2009

I go for CMOS battery problem, If the battery shows less than 3.3 volts on a meter replace it

  woodchip 15:37 24 Aug 2009

PSU cannot effect CMOS settings if the CMOS battery is okay

  the-george 22:25 26 Aug 2009

Replaced CMOS battery and reset BIOS and all seems to be ok again.
Think that what was happening was that after switching pc on it remained dead until a bit of charge built up in battery and then it booted giving the error message. By time I came to switch on following day then the battery was flat again and problem repeated.

Thanks for all suggestions

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