CPU-fan behaving strange

[benonikenobi]

so, I just built my new computer this weekend, CH7 with 3900x and a Noctua NH-D15 cpu-cooler. Since my ram was to tall for the two NF-A15-fans i switched the fan sitting over the ram to a NF-A12x25. I contected both the NF-A15 and NF-A12x25 to a splitter and then to the cpufan-header. I also have txo 140 mm fans as intake and one 120 mm as exaust in the back.

To my problem. I immediatly noticed that on or more fans sounded alot more than I would like. I tried setting all the fans to PWM in bios and set a rather flat curve (30% up to 65C and then a steep climb). After applying some of the fan noice went away but the loudest moice still persisted. After a lot of testing I came to the conclusion that it was the CPU-fan that was the problem. It didnt matter how low or high I set the curve in PWM, still as loud. However, when I tried DC-mode instead (fixed at 60% speed as lowest speed) the cpu-fans went quiet.

Is there a bug with the cpu-fan in pwm? Or is it because I connected two different fans to the same header? (shouldnt be a problem since noctua recommends changing one fan to a 120mm if you have to tall ram.

Any ideas??

Kind regads Benjamin

[gupsterg]

I can't say I have noted a bug with CPU-FAN header.

It shouldn't matter you have 2 differing fans on same header. When header is in PWM mode the 12V is constant, the PWM signal will be (xx)%, the fan has it's own IC which dedicates for (xx)% do (xxxx)RPM.

So as an example when header gives ~20% PWM, the NF-A15 will do (xxxx)RPM, the NF-A12x25 will do (yyyy)RPM.

Have you tried the UEFI 0002 released by Shamino?

[benonikenobi]

I can't say I have noted a bug with CPU-FAN header.

It shouldn't matter you have 2 differing fans on same header. When header is in PWM mode the 12V is constant, the PWM signal will be (xx)%, the fan has it's own IC which dedicates for (xx)% do (xxxx)RPM.

So as an example when header gives ~20% PWM, the NF-A15 will do (xxxx)RPM, the NF-A12x25 will do (yyyy)RPM.

Have you tried the UEFI 0002 released by Shamino?

Hi.

I´m currently on the 0002+ bios. It seems that the CPU-fans sounds as if they are going full speed (or at least almost) even though I set it to 30-40%, very loud. But as soon as I switch to DC and the lowest speed there is 60% the fans almost goes quiet.

In HWinfo the fans are reported going say 300rpm-ish when I set it in PWM-mode and 30%. but in DC-mode at 60% they are reported going at about 8-900rpm. The report in HWinfo seems to correspond to the % i set. But the actual speed and noice doesnt seem to ad up.

[gupsterg]

Hi.

I´m currently on the 0002+ bios. It seems that the CPU-fans sounds as if they are going full speed (or at least almost) even though I set it to 30-40%, very loud. But as soon as I switch to DC and the lowest speed there is 60% the fans almost goes quiet.

In HWinfo the fans are reported going say 300rpm-ish when I set it in PWM-mode and 30%. but in DC-mode at 60% they are reported going at about 8-900rpm. The report in HWinfo seems to correspond to the % i set. But the actual speed and noice doesnt seem to ad up.

Try this UEFI, you'll find it allows lower % plus increased CPU temp limit for fan profile, link.