Hello. I am (was?) the happy owner of a 65nm Athlon X2 4800+ (Brisbane core) on a KN9 Abit motherboard... A month ago my heatsink (Arctic Freezer 64 PRO PWM) fell onto the video card after one of the lugs from the retainer broke. The computer was on, I wasn't at home, my girlfriend phoned me telling me there was a strange noise from the computer, and now there's an alarm ringing... I immediately knew what had happened, and so she cut the power from the system quickly...

I feared the worst, but luckily the video card was not damaged and - after repairing the damaged AM2 retainer and fitting the old stock cooler - the CPU seemed well. I only tested a few minutes of SuperPi, it ran without errors and that was it. After a long search I finally found yesterday a Thermalright retainer (AM2RM rev.B), and was able to put back the Freezer... I also got a syringe of Arctic Silver 5, and so I wanted to check the temps... But running two instances of Prime95 (one for each core) gets the CPU temperature to 90 degrees C fairly quickly and the computer shuts down!

I have tried lots of things... Updated the BIOS from ver. 12 to 14 (temperature problems were among the fixes on the abit website)... Tried different programs to read the temperature... CoreTemp, SpeedFan, Sandra, AbitEQ...
I also put back the AMD stock cooler... the same. The computer is OK for light load, also some gaming... But two instances of Prime95 or SuperPi are getting the overheat protection to kick in after a few minutes only... And I could do that for days before the heatsink incident...

The CPU doesn't seem that hot when I touch it. The Freezer lets quite a bit of the heatspreader uncovered. And I know how 90 degrees C should feel. I wonder if the thermal diode was damaged when the heatsink fell off... Or maybe I crushed the processor when I attached the Freezer (is that even possible?)...

Some of you may say that incorrect temperature readings are a common problem with Brisbane cores. But they were just perfect in the beginning.
So, that's my story. I'm afraid it's a bit too long, maybe boring, and mildly incoherent in some places. But I've been trying to solve this all day, it's almost 3 AM where I live, and I can't shake the feeling that my CPU went south... Any advice will be greatly appreciated. Thanks in advance!

Have you tried reseating the HSF? If the HSF is not tight against the processor cap, temperatures can get very ugly very fast.

Is the fan on the HSF still spinning?

What's the temp while not under load?

Also, when the HSF fell away from the processor, was contact with the processor cap broke?

The HSF is seated correctly, in fact I've tried several times the Freezer and the stock HSF... Cleaning and re-applying Arctic Silver 5 each time...

The fan is spinning OK, going to full speed when the temperature reaches 55 degrees C ...

Idle temperature is good, around 35 deg. C ... It was always about the same.

And yes, the Freezer fell completely off... the CPU was on its own, no cooling at all... The alarm was ringing, but the computer didn't shut down. Perhaps it hanged because of the instant temperature increase. The shutdown works properly now, when it reaches 90 degrees gradually...

Oh and one more thing... CoreTemp is the only program that gives different (lower) temperatures from all other... But I think it's flawed, because it shows the cores at 14 degrees when idle... And there's around 30 degrees in the enclosure

I'd start saving for a new chip D: It seems that the one you're using is wanting to give soon & won't last long. Just my opinion.

Have you tried feeling up to the heatsink to see if it's actually getting hot? If the sensor is busted and it thinks it's getting hot, it will shut down just the same.

Did the HSF ever come into contact with any part of the motherboard (the video card apparently still works so that isn't much of a concern)?

I think I'd have to conclude that the processor was damaged (probably thermometer consider it is stable otherwise) when it overheated.

First of all, thank you for your suggestions and advices.

The HSF didn't come in contact with any parts of the mobo after falling, it just rested onto the videocard. Luckily it didn't short anything there...

@McFly: when I'm using the Freezer I can actually put my finger tips on the heatspreader because the base of the cooler is somewhat smaller than the IHS thus leaving the edges exposed. It doesn't seem hot at all, even when it shuts down. I'd say the IHS is at about 45 degrees when the programs (and BIOS) think it's at 90 degrees and shuts down. I even taken off the HSF seconds after thermal shutdown, and the IHS wasn't hot at all...

I'm thinking too of replacing the CPU... The only thing that I don't like about my 4800+ is the memory speed, that is around 714 MHz instead of 800 (something to do with the memory speed derived from CPU speed directly). I think there are certain models of X2 that clock the memory at 800 MHz (or close) but I forgot which they are...

Just some thoughts...

Before replacing your CPU, you might test it on a cheaper motherboard.

And, just being my normal cautious self, but before buying a replacement CPU you might want to first try replacing with a dirt cheap CPU...this is just in case there was other damage in the system and that is what eventually damaged the CPU.

Example, if the CPU power regulator was damaged...or if there is an internal compression short in a motherboard via, or something else visually undetectable.

That way, if the problem is not the CPU, all you've done is possibly damaged a cheap(er) CPU.

Thank you all for your feedback.

Well... Everything is OK now with my CPU temperature... But I haven't got the slightest idea why it is all working now...

I disassembled my computer... Checked if everything about the motherboard and CPU is ok visually... Then tested again with the old (broken) retainer and the stock HSF (even using the old Arctic Silver that was smeared on them)... And the temps were OK...
EVRIKA I said to myself... The retainer from Thermalright must be the culprit. But to make sure of that I mounted it again... And there it was, working perfectly even with the "new" retainer... As I said I have no idea why it is working now... It seems perfectly symmetrical, so I don't know if I mounted it the same orientation as it was before... Anyway I'm not going to reverse it again just to check... I'm happy that it's all going as it should.

I then tested with the Freezer, but I got mixed results... The temps were as high as with the stock HSF (around 63 degrees C in full load), it was much louder at full speed and when I poked around with my fingers to "feel" the temp of the heatspreader the temp jumped to about 75 degrees (I haven't tilted the Freezer, just touched the IHS)...

So I'm using the stock cooler now, very happily Prime95-ing right now at 65 degrees (my room is hotter than it was yesterday). And I can say that the Freezer is one of the worst computer parts that I bought... Breaking the retainer and causing all these problems really offset any of the advantages it might have had in the beginning...