Unusual Fan Control Setup in BIOS

Rebellious · Post by **Rebellious** » Mon Sep 15, 2008 7:05 am

Is this the front end for Asus Q-Fan control or is it something different? Mobo is an Asus A8M2N-LA very similar to M2NPV-VM.

I don't understand it, and it doesn't work as you would expect. The reason I adjusted it is because I noticed that CPU fan stayed at the minimum 1650 rpm no matter what the CPU load. In my mind, if you set "Acceleration starts at X" and "Switches to full speed at Y", then you've defined the fans' behavior, so I don't understand the purpose of "PWM Ramp Range".

I tried different settings, and I can get the fan to be very twitchy, to ramp up/down quickly and at irregular intervals in response to something, but I can't make sense of it. "PWM Ramp Range" does something in conjunction with the 'Start' & MAX setting but I'm not sure what. Changing it can cause spastic/aggressive 0%-100% RPM spikes or very slow and steady.

CPU and System fan are controlled with equal voltage, but in this rig the CPU fan can hit 5,500 rpm whereas case fan is a slow 1000 rpm 12cm. Fans don't hit full speed at the temp you set, and there is no explicit "desired temp".

Any ideas how this works?

Rebellious · Post by **Rebellious** » Sun Sep 21, 2008 6:15 am

I guess this BIOS setup doesn't make sense to anyone. The UI was written by somebody with poor command of the English language, so maybe if they described it better it would make more sense. I think it's the logic behind the Asus Q-Fan control.

Maybe this will help, here's what the choices are:

Initial/Idle Fan Voltage: 4-12 Volt in Â½ volt increments

Acceleration Starts at: 25-70 degrees C

Switches to full speed at: 30-85 degrees C

PWM Ramp Range: 2, 2.5, 3.33, 4, 5, 6.67, 8, 10, 13.33, 16, 20, 26.67, 32, 40, 53.33, 80 degrees C

FlorisNielssen · Post by **FlorisNielssen** » Mon Sep 22, 2008 10:01 am

Try switching between extreme values. (Just change one setting.) That way you'll notice the difference and the impact of one setting.

I'd suppose you want to set the initial voltage to your fans starting voltage or a bit higher, cause that would be the minimum voltage the fans will always be receiving.
The acceleration to something like 50 degrees, so the fan usually won't ramp up. Full speed at 65.
The PWM ramp range to the slow acceleration you were talking about. Would probably be my optimal setting.

Rebellious · Post by **Rebellious** » Sun Nov 02, 2008 8:08 am

Thank you. I got it working, I just don't understand the meaning of the "PWM Ramp Range" setting in degrees.