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Lately my CPU fan has been roaring along at 100%, and I'm having trouble figuring out why. It will, at one moment, be running quietly, and the next moment blazing at 100%. I haven't changed anything in the BIOS settings, nor have I installed any new hardware. The heatsink itself is not dirty, its got a little dust in it, but not enough to obstruct airflow. Using temperature monitors tells me that the CPU is hovering at a constant 26-29 C. Its strange because it's never done this before, and I'm worried that running it constantly at 100% will end up breaking it.

I can control the fan via SpeedFan, but my concern is that this might be a sign of a bigger problem. Any thoughts on this?

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When that happens what does your CPU usage looks like? – Mxx Mar 8 '13 at 4:53
Did you consider the change in room temperature? Has there been a change in your usual room temperature in recent times? – Masroor Mar 8 '13 at 6:34
CPU usage doesn't look out of the ordinary for what I'm doing (just playing EVE Online), and I don't see any spikes or drops in CPU activity that coincide with anything that I'm doing, but I'm only using SpeedFan's built-in meter to test that. There haven't been any unusual changes in temperature, at least none that I can feel. – cornjuliox Mar 8 '13 at 13:28

I know from experience that there is a small delay between heavy CPU activity and CPU-fan activation. (the heat takes a while to built up) So check what process had a spike just BEFORE the fan kicked in. Second, is your CPU multi-core? then it's possible that the fan is responding to heavy load on ONE of the cores. EG: 12.50% for a process on an 8-core could mean it's using one of the cores at max.

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The multi-core issue could be the origin, I agree. I suggest AIDA64 ( (trial version available) for a better core-specific thermal measuring. – Sopalajo de Arrierez Jun 10 '14 at 22:19

This is usually due to thermal thresholds set in the BIOS or Intel/AMD desktop app. In my experience, unless you are doing crazy processing it is usually dust that clogs up the fan which you can fix with a can of compressed air.

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