Question ASUS motherboard BIOS fan control FIX rpm for CHA_FAN?!


Jul 3, 2016
Hi all,

So I'm pretty thrilled at the moment, because I just learned that I can't seem to be able to set my CHA_FAN(1-3) headers to fix rpm mode from BIOS's qFan Control as around 72-75c it's 100% all the time... which is am irritating. I know there was a fix rpm setting on the AI Suite but why would I install any 3rd party software for something as simple as fan control. If I wanted that I would have bought all corsair/nzxt fans and plug them in the commander/grid. Is there really no way for an z390 motherboard to set the fans to constant rpm mode of 50%? CPU fan's I couldn't care less but if I try to OC my CPU all my case fans are on 100% and it's literally loud as a jet engine which is unacceptable...
There are lots of models in the ASUS Z390 series, so we're not sure exactly which one you have. But you should recognize that AI Suite is ASUS' own utility for fan (and other) optimization. The basic issue here is that you CAN configure fans headers in BIOS Setup and observe their speeds, but you can NOT do that while doing real work. So instead if you install and use the AI Suite tool, it is a Windows app you can run on your screen while doing other work and thus "see" their operations in a "real world" workload. Then you can use its tools to adjust the fan headers if you wish.

You should realize also an important fact. The automatic fan speed control systems in any mobo are based on keeping the TEMPERATURE of certain components under proper control. The CPU_FAN header concentrates on the temperature measured by a sensor inside the CPU chip. The SYS_FAN or CHA_FAN headers use a different temperature sensor on the mobo to guide them. If your system fans are running up to high speed when you OC your system and cause it to generate more heat, that is because the inside of your case is getting hot and your system NEEDS more cooling! If you force your fans to run at a fixed low speed for quiet operation, you will also force all your components to run at too high a temperature and cause more rapid aging even if you don't go so hot the system throttles itself for self-protection.

There is one other detail you should check for though, but we cannot give you exact instructions because we don't know which mobo you have. On many mobos for configuration of the CHA_FAN or SYS_FAN headers you have an option to select exactly which temperature sensor is used to guide that header. Sometimes they are set to use the sensor inside the CPU chip for all fan headers. BUT for the CASE ventilation fans, you really should configure those headers to use the temp sensor on the MOBO, not the one inside the CPU chip.