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CMOS not holding information

By erothoff ·
I have a few motherboards that keep loosing their information in CMOS and opererates in default mode. This seems most common in the multi-function Motherboards. (That have NIC, video, etc built-in. Changing the normal (round flat) CMOS battery does not help. While I would like to try the old external CMOS batteries that we used for the 486's, big with the speaker type connection, these motherboards on have that option. (These are mostly motherboards that support AMD K6 processers, Super Socket 7)
Any suggestions on how to solve this problem?

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by maxwell edison In reply to CMOS not holding informat ...

My first thought was, of course, a bad battery. But the fact that you changed them, in several different motherboards, no less, suggests something else. I would then think that the battery contact was dirty, but then again, on multiple motherboards?

I would suggest a couple of things. First of all, what about the possibility of a BIOS virus? You don't hear of them too much anymore, but these are older motherboards. Check Symantec, McAfee, or Trend Micro Web sites for some detection tools.

Another thing you could try is a BIOS flash. Updating to the most current BIOS version might resolve any conflict issues you may have.


(REMOVE SPACES that may sneak into the pasted URL.)

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by TheChas In reply to CMOS not holding informat ...

The old 486 motherboards had much higher current requirements for the backup battery than the newer motherboards that use the coin cell style batteries.

The reason for the plug-in battery was so that you did not have to unsolder and resolder to replace the NiCad battery they used.

Unless the coin cell batteries are being drained, it is likely not a battery problem.

In addition to Max's suggestion of a BIOS virus, many of these motherboards used a socketed DIP style BIOS IC.

Carefully remove and re-seat the BIOS IC.

It would not hurt to check the clear CMOS jumper.


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by Kinetechs In reply to CMOS not holding informat ...

Take a look at the MB manual for jumpers for CMOS reset. It may be shorted with a jumber and just needs to be moved.


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by erothoff In reply to

Sorry, but I had checked that item first. That was my first assumption

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by wcp In reply to CMOS not holding informat ...

It is hardware problem and now it?s most likely due to RAMs.
Exchange the RAMS with known good ones from a different computer. Test one computer at a time.
Make sure the computer is clean inside.

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by erothoff In reply to

Sorry, but I have changed RAM many of times, but for different reasons. That is not the problem.

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by RCOM In reply to CMOS not holding informat ...

Agree with suggestion to check the jumper that clears the CMOS and making sure its not set to pins 2-3.

Does the batteries that your installing have the full power? Can be checked using a meter.

A couple of years ago I sold a few I think AZZA motherboards that had this problem. By doing a simple point to point check with a meter I found out that it was a failed doide that was draining the battery. I couldn't find replacement diodes so a cheap resolution was to keep the damn things running all the time until I could get other boards.

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