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What is 'CPU min fan speed' setting in BIOS?

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June 29, 2013 5:11:17 PM

In the BIOS settings for my MSI G41M P33 mb, I see 'CPU Min. Fan Speed (%)'.

What exactly does that mean? Is that a percentage of its maximum speed capacity?

I also see 'Target' [something, cant recall exact words]. Is the the target temperature after which the fans should speed up to bring temp down to the 'target'?

This is the first time I've explored these settings and I'm trying to learn, if anyone can help me understand, I'm very appreciative. Thanks!
a c 198 à CPUs
June 29, 2013 5:20:06 PM

It's the setting by which if it detects lower than that it will alarm and / or shut down machine.
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a c 173 à CPUs
June 29, 2013 5:20:38 PM

You're basically right on both counts, though the maths it does is a little bit more tricky.

Min fan speed is the minimum percentage of 12V that the fan needs to start spinning - if you set it too low, your fan won't start, and your motherboard will likely refuse to boot because it can't detect a fan.
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June 29, 2013 5:31:30 PM

Ok. Thanks for the explanations. Why would my cpu fan be running at or above 1580 (rpm) at all times ? Is that some sort of min. rpm for the fan? It is a very noisy fan (new) & I'm trying to figure out how to reduce the rpm when the cpu is cool. Thanks.
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June 30, 2013 1:14:45 PM

Is the cpu fan speed a function of the fan itself, also? Or solely controlled by the BIOS?
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a c 173 à CPUs
June 30, 2013 4:34:38 PM

The actual fan speed is caused by how fast the fan spins under a given voltage. Your BIOS sets the fan to say 25% of 12V, and the fan then spins at whatever that causes it to spin at, based on how it's designed.

You should be able to change the fan profile in the BIOS.
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June 30, 2013 11:43:25 PM

Someone Somewhere said:
The actual fan speed is caused by how fast the fan spins under a given voltage. Your BIOS sets the fan to say 25% of 12V, and the fan then spins at whatever that causes it to spin at, based on how it's designed.

You should be able to change the fan profile in the BIOS.


I have the option in the AMI bios to 'set 'CPU Min. Fan Speed (%)' - but it appears to do absolutely nothing to fan speed (at least I am unable to slow it down below 1500). Any ideas as to what else I can do? It is an MSI G41M P33 motherboard with AMI bios just purchased to replace a failed mb
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a c 173 à CPUs
June 30, 2013 11:59:38 PM

The fan in question is a four-pin fan plugged in to the CPU fan header, correct?

It's possible that it's not reducing the fan speed because the fan needs to be going that fast to keep it cool.
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July 1, 2013 12:25:32 AM

Someone Somewhere said:
The fan in question is a four-pin fan plugged in to the CPU fan header, correct?

It's possible that it's not reducing the fan speed because the fan needs to be going that fast to keep it cool.


Yep, it's a four pin connector.
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a c 173 à CPUs
July 1, 2013 12:31:49 AM

Hmm. I'd guess that it's not slowing the fan because the fan profile is set relatively aggressively, or because you've got poor airflow elsewhere and thus need a faster fan on the CPU.
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July 1, 2013 8:19:52 AM

Someone Somewhere said:
Hmm. I'd guess that it's not slowing the fan because the fan profile is set relatively aggressively, or because you've got poor airflow elsewhere and thus need a faster fan on the CPU.


The only thing I can think of is that there is a *little* bit of dust down in the cpu fan when i look inside the pc case. Could that be enough to cause it to get 'hot'? The cpu runs at about 29 to 34 C temps but the fan is always on 1500+ rpm. BTW, is that rpm simply a normal minimum RPM for cpu fans?

Can I just hold my standard home vacuum 'crevice' attachment up to the cpu fan to vac it out? Or is that too risky for static??


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a c 173 à CPUs
July 1, 2013 5:05:15 PM

1500RPM isn't too far off normal, though it depends on the size of the fan - tip velocity is probably a better indicator. I've got 40mm fans that are pretty quiet when doing 4K RPM.

Are there any options in the BIOS for changing the speed profile?
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