Question My PWM fan is fine in BIOS but I can't see it in OS?

Feb 23, 2019
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I have a Noctua PWM industrial 120mm fan on the back of my case connected to chassis fan header 2 on my ASUS Z170-I Motherboard.

In BIOS I've selected PWM mode on the header and it seems to be fine at 20%. Just where I want it.

However, when I boot into OS my settings seem to have been completely ignored.
The fan instead of a minimum RPM of 20% is alternating from being completely stopped to 5% and back and forth and back and forth.

When CPU is under stress the fan spins up to a slow speed. I'd say around 30% maybe.

Basically, when I'm in OS the fan curve IS NOT what I put down in the BIOS.

Furthermore,
Software such as AI Suite and Speedfan don't even think it exists.

Some pictures:
View: https://imgur.com/a/soqJjcp


Any idea what's happening here?
 

Grobe

Distinguished
Jan 22, 2009
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Ok, so it basically means that the Asus software owerrides any settings you've made in bios.

I think you just need to accept that and try to find a setting in the Asus software that makes similar fan speed/temperature profile, aka do things over again.
 

Karadjgne

Titan
Herald
According to the pic, it's showing a (left side) rear exhaust connected to cha_fan 2, cpu fan (middle) and the ? fan at cha_fan 1. Have you used the fan tuning button yet? AI Suite doesn't auto-detect fans by itself, it only registers fans it's used by tuning between position, speeds etc.

With SpeedFan, you'll actually have to manually go searching for the fan as there's several different addresses SpeedFan uses between the different Isa addresses. It too doesn't always detect fans without some user input and adjustments.
 

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