Question CPU fan going up and down

Jun 19, 2021
2
0
10
0
Hello, my pc fans are going up and down. I was wondering whats the best settings for Q-fan controlling in bios. I've got 3 fans in my chassi and 1
CM Masterliquid ML120L ARGB for the CPU. Have to mention that i have never controlled or tried to change any settings in Fan controll so The fans profile are set to standard i don't know if thats the best settings to use cause there i more options.

So in the 2 Chassi fan Q-fan control i have two options either DC mode or PWN mode which one would be the best to use? Also which settings should i use for the Q-fan source CPU or motherboard?

Would appreciate it alot if someone could help me out, sorry for my bad english hehe ..
 
Last edited by a moderator:

iPeekYou

Distinguished
Jul 7, 2014
394
76
18,790
10
Hello, my pc fans are going up and down. I was wondering whats the best settings for Q-fan controlling in bios. I've got 3 fans in my chassi and 1
CM Masterliquid ML120L ARGB for the CPU. Have to mention that i have never controlled or tried to change any settings in Fan controll so The fans profile are set to standard i don't know if thats the best settings to use cause there i more options.

So in the 2 Chassi fan Q-fan control i have two options either DC mode or PWN mode which one would be the best to use? Also which settings should i use for the Q-fan source CPU or motherboard?

Would appreciate it alot if someone could help me out, sorry for my bad english hehe ..
Hi there, and welcome!

If you want to setup your fan curves, you need to find how fast the fans spin which noise you can comfortably tolerate, and set it as the maximum percentage value on the fan curve (the rightmost and highest point on the curve). For temperature value, I use 78°C since that's just a bit beyond my worst case scenario temp. Depending on which CPU you have, you might set a higher or lower value that's a good 7-10°C out of maximum allowed temperature.

From then on, I'd recommend setting the other points in a steep curve that gets steeper after each stepping. This is mostly to prevent thermal runaway scenarios (where it gets too hot too fast for the fans to keep up), and maintain a low noise at low heat loads. The exact temperature value for each points don't really matter, and a lot of times you might need to tweak the fan curve to best suit your noise and performance needs.

DC or PWM control depends on the fans connected to the header(s). 3-pin fans need DC mode for speed control, and 4-pin fans need PWM. Setting PWM control for 3-pin fans will cause them to always be at 100% speed, and DC control for 4-pin fans will damage the PWM controller inside the fans.

I personally use the same curve on CPU header and system fan header simply because I can't be bothered and I can live with the noise. YMMV, you can set a more aggressive fan curve (steeper and/or having a lower maximum point) if the case fans are quieter, or vice versa.
 
Jun 19, 2021
2
0
10
0
Hi there, and welcome!

If you want to setup your fan curves, you need to find how fast the fans spin which noise you can comfortably tolerate, and set it as the maximum percentage value on the fan curve (the rightmost and highest point on the curve). For temperature value, I use 78°C since that's just a bit beyond my worst case scenario temp. Depending on which CPU you have, you might set a higher or lower value that's a good 7-10°C out of maximum allowed temperature.

From then on, I'd recommend setting the other points in a steep curve that gets steeper after each stepping. This is mostly to prevent thermal runaway scenarios (where it gets too hot too fast for the fans to keep up), and maintain a low noise at low heat loads. The exact temperature value for each points don't really matter, and a lot of times you might need to tweak the fan curve to best suit your noise and performance needs.

DC or PWM control depends on the fans connected to the header(s). 3-pin fans need DC mode for speed control, and 4-pin fans need PWM. Setting PWM control for 3-pin fans will cause them to always be at 100% speed, and DC control for 4-pin fans will damage the PWM controller inside the fans.

I personally use the same curve on CPU header and system fan header simply because I can't be bothered and I can live with the noise. YMMV, you can set a more aggressive fan curve (steeper and/or having a lower maximum point) if the case fans are quieter, or vice versa.
Where do i setup the facn curves? I haven't had this problem before, I don't know why one of the fans are first silent and than goes loud and than back to normal.
 

iPeekYou

Distinguished
Jul 7, 2014
394
76
18,790
10
Where do i setup the facn curves? I haven't had this problem before, I don't know why one of the fans are first silent and than goes loud and than back to normal.
In the BIOS, under Q-Fan or Smartfan, or something along those lines.

Re-check the offending fan's connections, and check whether your temps spike during the fans ramping up and down. If everything works fine, then maybe set up a less aggressive fan curve or add temperature offset in the BIOS fan control to slow the fans' change in speed.
 

Paperdoc

Champion
Ambassador
Post back here the maker and exact model number of your mobo so we can look up its manual and give precise advice. For background ...

The default setting for all fans is called its Automatic or Normal PROFILE. That is the strategy the mobo uses to decide what speed the fan should run. It is tied to a temperature sensor (one inside the CPU chip for CPU cooling control, and a different one on the mobo for case fan control). Each is a TEMPERATURE control system that manipulates fan speed to achieve a temperature target. Each has a "fan curve" it uses of what speed to run the fan for what temperature the sensor reports.

A different setting for a fan header called its MODE specifies HOW tyhe fan speed should be controlled once the Profile setting has decided what that speed should be. It is to be set to Voltage Control Mode (aka DC Mode) for 3-pin fans, or PWM Mode for 4-pin fan.

ALL of these systems are supposed to change the fan speeds automatically as measured temperatures change as a result of workload changes. So CHANGES of fan speed are NORMAL. Many of them do this step-wise and not along a smooth gradual curve. So sometimes it happens that the normal range of operating temperatures is right near where a step-change of fan speeds is called for. Thus small fluctuations of temp can produce noticeable fan speed changes repeatedly. If that is your case, you may be able to alter the temperature that calls for these frequent changes by specifying your own custom "fan curve" to replace the default settings. Most mobos allow this now. With details of your mobo, we can advise how you can do that.
 

ASK THE COMMUNITY

TRENDING THREADS