# power fan header vs system fan header



## cly (Jul 17, 2010)

I can't figure this out.  My gigabyte mobo has a system fan header and a power fan header.  Both plugs are the same. They are both 3 prong: ground, 12V, and Sense.  What is the difference? Thanks


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## cly (Jul 17, 2010)

Well I decided to use the power fan header but if anyone could answer my question that would be great.  The other questions that I also have is that my Bios says the power found speed is zero RPMs even though the fan is working.  any ideas why?


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## AsRock (Jul 17, 2010)

Not 100% sure but ones called power as some PSU's have a fan cable so you can get a reading of it.  Were the others can be controlled though bios or some though software.

Although i have never used mine for that purpose and with Maximus mobo there is not speed control  in bios either.


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## Timonthy (Jul 17, 2010)

I would use the SYS_FAN, the PWR_FAN looks like an header for some PSU's fans.

Both should work, but with the PWR_FAN header the fan is probably gonna end-up running at full speed all the time as the board not having direct control over it.


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## TheLaughingMan (Jul 17, 2010)

I think the headers are the same on the mobo, but the fans you are using are different.  The fan on your CPU cooler most likely has the extra feature of allowing the mobo to change its speed dynamically.  Most case fans are cheaper and do not include this feature, which is 1.  Why it will run and full speed. 2.  The sensor header is just used to check to see if the fan is running or not.

So I think you are looking at it from the wrong perspective.  I could be wrong though as I am not sure if I remember that correctly.  You can test the theory by switching them and seeing the BIOS then says the CPU fan is at 0 RPMs and the System fan is is being reported.


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