CPU frequency out of whack...

[fink]

What are things that would cause the CPU frequency setting in BIOS to spontaneously change on its own?

My friends PC stopped booting this am so she had me look at it.. it just wouldn't boot.. CPU fan spun for a second as did the Power Supply fan but then it just sat there.. no beeps, no monitor, no anything.

My first inclination was the PSU or maybe the MBoard. I had a spare PSU and switched it out but it made no difference.

Nothing I could do with the MB except look for blown caps and make sure everything was seated properly. All was ok
with it too.

On a hunch I took out the CMOS battery to test the voltage and it was what it should be but in taking the battery out I also reset the CMOS to factory and then when I booted once more this time it actually got into the BIOS and stopped... the message was it had started in safe mode because the CPU freq was improperly set. I set it to what it should be (which is what was showing now by default) and rebooted and lo and behold all was fine.

So, the question is what would cause that?

tnks.

[Steve R Jones]

1. User messing around in the BIOS

2. Battery not being as good as you think it is

[fink]

1. User messing around in the BIOS

No, she didn't know what a bios was let alone get into it.

2. Battery not being as good as you think it is

Tested full power on my multimeter. Would corrosion
on the contacts cause that?

[jdc2000]

3. Power spike messing up BIOS CMOS settings. I have had that happen before.

[fink]

That's a possibility.. we've had unsettled weather lately and
a few days ago there was a major power disruption in a nearby
neighborhood (though she'd used the PC since then without issue)

[Steve R Jones]

Odds are you might not ever know....Unless of course it starts happening on a regular basis.

[SuperSparks]

Corrosion on the contacts can definitely cause it though. I always give them a good rub any time I remove or change a battery.

[crunchie]

Don't forget that a near depleted battery can still show the correct voltage. I have had car batteries that will not crank the motor still read a full 12 volts on a multimeter, until I turn the key to start, then the volts plummet.

[fink]

It's been ok so far but if it happens again I'll replace the battery and clean the contacts better.

[lgbpop]

It also could be that you didn't F10 on the way out of the BIOS, or any number of other little niggling things.

If this is the first time you've fiddled with this computer, make sure the PSU's not plugged into a switched outlet. I don't want to admit how much time I've wasted looking for profound solutions to gremlins, only to discover this.

[fink]

didn't F10 on the way out of the BIOS

The problem started before anyone ever entered the bios. (It used to be my PC but I gave it to her a year ago and the last time I was in the bios was longer than that)

a switched outlet

She had some painting being done in her apt and had moved the computer around and temporarily used a different ac outlet but it wasn't switched... that was one of the first things I checked because we have identical units and I've done that accidentally as well <rolleyes>.

The symptom manifested itself even after unplugging/replugging the PSU from ac power... When the power button on the PC was engaged all that would happen (which I could easily see with the case covers off) was the CPU and PSU fans would spin for about a second and then just stop before anything would appear on screen and well before any beeps would have occured. The diagnostic/power LED attached to the MB was indicating no problem.

I'd always believed that a PC would usually boot even with a dead battery but would default to factory BIOS settings... that's why
it wasn't the very first thing I checked. Since it seems to have been battery related I'm thinking it may have been a corroded contact problem and while the computer was being moved for the painting it was jarred and very quickly may have created an arc which sent the BIOS settings into fits.

I do recall replacing the battery on the MB when I had it but I can't remember when exactly.. may have been 2-3 years ago.

[lgbpop]

Oh, got it now, I misunderstood. Only other thing I've run into that manifested itself like that was a loose HSF not making proper contact with the CPU. That was twice, on old P4s.

[fink]

Well it happened again. I replaced the battery, cleaned the contacts, removed the HSF, cleaned it and applied new thermal compound (it seems to sit quite tightly) but it still refused to boot. However, after the 24th time I hit the on switch it did finally boot so now she's backing up all her important files to an external drive while it's still running.

No specific idea what the problem is but I'm leaning heavily towards a nearly fried Motherboard.

[lgbpop]

Sure is an odd problem. Reminds me of playing around, overclocking processors for the heck of it and sending a computer into lalaland. Took repeated starts to get it to boot, then when it did it was on the fail-safe defaults.

[jdc2000]

Bad capacitors?