Question CPU fan spins so fast at startup, what it does?

Apr 11, 2019
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I have a i7 4790k and I'm happy with it, (no overclock, 4.0Ghz) however this been like this since we got from the store, fans spins up so fast at boot/startup and then goes down to its normal speed in seconds, I know its normal, but what it does? A friend of mine told me "cpu does that to check stuff on motherboard, like everything is in order or not etc) is this true? It can detect anything if its wrong placement or errors like that?
 

hotaru251

Reputable
Oct 30, 2014
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same can happen with GPU's.


when you start system up they would go at w/e base speeds are, but if your fancurve in bios or w/e) are normally higher they will rev up fast to get back on track.

its normal.
 

Satan-IR

Honorable
Apr 18, 2014
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The fan usually does that if it's voltage-controlled. Fans supporting PWM (headers has 4 pins) usually don't rev to max even at boot.

Some systems/BIOSes try to see if fans can get to max speed during POST. Some motherboards have settings for this and if the CPU can't reach the set threshold RPM then there will be a warning/error. If the fan can't hit that RPM at boot the user can reduce the threshold value to avoid the warning/error.

You don't have to worry about it as long as the fan works and it revs up and down according to CPU load/temperature.
 
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Fans often run at full speed at initial power on until the BIOS correctly reads the speeds/temps, and scales the fan speed back somewhat....(as long as the fan profile in BIOS allows fan profiles)
Been quite normal for a couple of decades... :) (Yes, I'm old!) :
 

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