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Many computers spin up the CPU fan to high speed the moment they are powered on, even before POST, before settling down to normal operating speed.
While this behavior seems normal for the most part, why do computers do this, and what purpose does it serve?
(Note that on at least one computer I've worked with, including an old Sony VAIO desktop, the fan doesn't spin up until after about one second from the time the system is powered on. The fan revs up for a moment, then settles down.)
2How about this: Because POST wants to see if it can properly sense fan speed. – Daniel R Hicks – 2014-12-22T01:47:02.677
I don't understand these answers. The fan running at high is ridiculous and there is no need for this. Most computers at boot up run the CPU and other fans at a normal speed period. No concern with hurting the CPU, because if the CPU would heat up then the speed could be increased steadily. There should be a fix to the fast CPU at boot up. Check the BIOS. – None – 2012-07-22T01:31:35.193
@KevinSmith, > No concern with hurting the CPU, because if the CPU would heat up then the speed could be increased steadily. What if the system is messed up? How exactly would it “steadily increase the fan speed” then? > There should be a fix to the fast CPU at boot up. Yes, there should be, but isn’t.
– Synetech – 2012-07-22T01:55:25.697