CPU became slow all of a sudden

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Apr 10, 2010
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18,510
I have a home-built system (Abit UL-8 with Athlon X2 3800) which was working fine for about 2 years.

Then, a few days ago, it started locking up (while watching movies), had a hard time booting up, and if it did, it was dead slow.

I suspected the harddrive, but had the same issue with three different ones I put it. Installing Windows XP on one of them took about a whole day!
I removed the DVD-drive, tried a different video card, swapped the memory, the fans are working, but it is still slow as hell.

It does seem to work (no errors are popping up anywhere), but just VEEEERY SLOOOOW. Just booting up Windows (totally clean - nothing installed) takes about 15 minutes.

Running the Passmark tests gives me result about 100 times slower than on another machine with the same CPU (e.g. the CPU - Integer Math test may return a score of over 200 on the working machine, but a score BELOW ONE on the buggy one!).

Now - the only thing I didn't swap so far were the motherboard and CPU.
But can it really be that a MB/CPU breaks in a way that they still work "normally", just extremely slow???
Those seem to me like "go / no go" items, that either work fine, or not at all.
 
Check the temperatures of the CPU. It sounds to me like it is throttling itself due to overheating.
Solution to that are:
-clear all dust from the system using a can of compressed air. especially from the CPU heatsink.
-reseat the heatsink with new thermal compound if still running too hot.
-ensure there is proper ventilation and the CPU fan works.

Generally you want the temperature on load to be under 60C but I can see the CPU throttling itself at maybe 70C (I am unsure of the temperature where it begins to throttle)
 

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My CPU temperatures are actually well below 40º (as checked with CoreTemp), so that doesn't seem to be the issue.

Also, the heatsink is pretty clean, and since the slowdown already happens right when I start the PC, it seems unlikely that it's a heat-related issue (as the CPU didn't even have time to heat up yet).
 

hundredislandsboy

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It almost sounds like your PSU got bumped on the rear switch to 220 and you're 110 volts.

Sounds like VRM dying.


Take out a flashlight and magnifying glass and inspect the capacitors. If you know how to use an oscilloscope, measure the VRM ripple if you're not sure about the capacitors.
 

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I'll try a different PSU...

It's just a bit complicated, as the spare PSUs I have don't have the power connectors to hook up to the harddrives that have an OS on them, and the harddrives with compatible connectors don't have an OS (so I guess I'll have to install XP yet another time - hopefully it won't take a whole day like it did the last time).
 

hundredislandsboy

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You can get molex splitters, or molex splitter into 2 SATA power connectors.

Try a CMOS clear also in case it's your BIOS getting corrupted, especially hard drive settings.

How much is there? Could be using your hard drive a memory which will bog down the system.

Or your hard drive is so fragmented?
 

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Well, looks like a MB/CPU can break in a way, that it just becomes extremely slow...

I tried another PSU, and installing Windows took just as long as with the original one (3 hours to go from the "39 minutes left" message to the "34 minutes left" one...), and even resetting the BIOS didn't make a difference.

I guess I could still try to swap CPUs from one machine to another, but with the prices for used ones in that performance range, it's probably not worth the hassle.

Thanks everybody for the feedback!
 

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It's the motherboard, after all...

I couldn't resist another test, and swapped CPUs with another machine (very similar MB/CPU), and low and behold - the CPU from the "bad" machine now behaved just fine, and the CPU from the "good" machine ran in slow motion.
 

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