ASUS Q-Fan BIOS Minimum Fan Duty Cycle

[PaulCa]

While booted into Windows I use Argus Monitor to control most of my fans and can actually stop most of them when temps are low under desktop use, I still spend a large amount of time in Linux where there is no current driver for the ASUS X470 sensor or fan control chips. So I have to use the BIOS level Q-Fan controls.

The issue is that when I run the QFan fan profiling it comes back with whacky minimum duty cycles. One of my case fans reports minimum duty of 42%, the BIOS will not let me set a lower duty. At 42% the fan spins at 1000rpm and makes noise.

I am looking for a way to override that, so I can set 0% in a manual curve.

I have 2 240mm radiators, CPU (front intake) and GPU (roof exhaust), plus I have 3 case fans, 2 intake, 1 exhaust. When all are set to 100% it sounds like a rack server but maintains impressively low temps. However when all the case fans are off and the rads are on minimum it will still run bench marks with only a slight impact on boost clocks before the GPU actually winds the rad fans up at 60*C.

So in short I have no need for my case fans to be running at 40% when I'm browsing the web in Linux, it's annoying.

As a side issue, neither radiator fans will stop. The Corsair H100x fans will run at 650rpm even if you send a 0% duty cycle. I do not know if this is because it's connected to the mobo CPU fan header and it's over-ruling me or if it's the fans.

The GPU rad fans (NZXT Kraken x52 default fans) will also not stop and spin at a minimum RPM regardless of what I tell them to do. These are controlled by the GPU BIOS (or MSI Afterburner), neither stop the fan completely and they continues to spin at 500 RPM. This might be an artifact of the fractal designs fan hub which powers the GPU rad fans and the G12 bracket fan. The GPU is capable of stopping it's air cooler fans.

I could probably live with the both rads fans spinning at minimum RPM as they are pretty quiet and provide basic case air flow, but I do need to address the case fans spinning at 30-40% duty caused by Q-Fan.

Does anyone know a way to over-ride the fan profile to get 0% as an option?

 

[LuckyBenski]

As a general rule, PWM fans are designed such that if you offer too low a duty cycle, they will drive themselves in order to keep spinning. This usually results in a minimum speed at about 30% duty cycle and lowering it any further changes nothing.

For recent GPUs that can stop fans, AFAIK the fans have to be designed to accept this but your minimum speed still probably lands around 30%.

You've said you can stop fans using Argus bit later said you can't seem to stop any fans. I'm guessing the GPU air cooler fans are no longer mounted as you've gone to a CLC?

Voltage control can often stop fans but PWM speed control can only very rarely do this.

I was under the impression Asus Q-fan had a manual curve option but I haven't used it because I use Speedfan. Have you tried quiet mode?

 

[LuckyBenski]

FWIW I use a combination of voltage control and PWM speed control. Inline resistors might be your best bet, as they will limit max speed (which you say is noisy) and lower the overall speed range proportionally.

I also haven't figured out fan control in Linux

 

[PaulCa]

I think the spec allows fans to stop under 30% or keep spinning at 30% up to the individual fans.

All my Arctic F14s stop < 30% duty with Argus monitor. The CPU radiator fans (Corsair SPs) don't. That is either the motherboard over-riding the 0% duty command due to them being on the CPU fan header or it's the fans themselves. I could test by swapping them to a case fan header.

The GPU fans are wired off the GPU header to a PWM fan hub in the case, so they can safely drive 3 fans without overloading it. The original GPU air cooler fans would stop, and I can see in MSI Afterburner it is commanding a 0% duty, but the fans remain at 500rpm. This is either the fans themselves or the fan hub refusing to go below 30%.

I'm not concerned with the high noise of full speed fans as they never come close when controlled on temperature, they only get over 50% if I force them with a manual setting of 100%.

I'm more annoyed with Q-fan claiming some of my fans have a minimum duty of 42% and refusing to allow me to set a duty lower. This results in 2 of my case fans spinning at 1000rpm in Linux when they don't need to be. You can set a manual curve, but the minimum speed is based on what it senses as the fans minimum duty. Only alternative is to disable the fan completely.

It's not really a big deal. There is a hack I found if I keep spinning a fan with my fingers while Q-Fan is sensing it's minimum speed the it will give me a lower minimum, but I can't do that with all the fans at once.

As an aside point I think I found a weakness with allowing the GPU BIOS to use it's default fan curve. It doesn't spin the radiator fans up until the GPU gets to 60*C, but after gaming for an hour like this the card went into some form of panic throttle and dropped the clocks to about 800Mhz, so I think the VRAM or VRMs are overheating. If I let MSI afterburner use it's auto fan control the GPU recovers, temps drop 10*C and it's stable. I guess the GPU fan curve is designed for it's air cooler and there isn't enough heat sink for the VRAM and VRMs at minimum fan speed with the G12. 54*C exhaust temp for the radiator is amusing though!