[aunola]

Hello,

I have built a workstation that I am getting some strange fan behavior on. All fans - CPU and chassis - are periodically ramped up to near max. speed for a few seconds, then down to lower, expected speeds for maybe 10 seconds. This cycle repeats forever.

I have seen others having this problem with Supermicro boards, where the solution was to adjust fan thresholds. This does not work for me with my GIGABYTE motherboard.

To give you a chance to see if I messed something up, here is what I have:

GIGABYTE MZ72-HB2 mother board
2 x EPYC 7542 CPUs
2 x Noctua NH-U9 TR4-SP3 coolers
Fractal Design Torrent cabinet

The cabinet has a Nexus 9P Slim Fan Hub:

Connected the two CPU cooler fans to the motherboards CPU0_FAN/CPU1_FAN connectors.
Connected the cabinet hub's 'GND FG PWM MB' to motherboard SYS_FAN1 connector.
Connected the cabinet hub's FAN1 to the 4-pin connector of one of the 5 cabinet fans.
Connected the remaining 4 cabinet fans to the FAN6-FAN9 connectors on the cabinet hub.

There is nothing in the BIOS allowing fans threshold adjustments.

In BMC I can see the fans sensors (2xCPU and 1 system) and adjust a lower critical and non-critical threshold for each of them. They are quite low out-of-the-box (150 and 350 rpm). I tried setting them as low as possible (50 rpm). No change in behavior.

If I remove power from the hub so that only CPU fans are active, I get the same oscillating behavior.

I am all out of ideas as to what to do.

If you have any suggestions how to solve this problem, I would very much like to know.

[JBeilke]

The solution for me was a fan hub (Noctua NA-FH1) together with a fan controller (Noctua NA-FC1). All fans are connected to the fan hub. Nothing is directly connected to the motherboard.

[aunola]

Thanks for your reply. I was banking on making automatic fan speed control by MB work. Manual control would be last resort.

Did you have this problem with the exact same MB?

[JBeilke]

It's still automatic since the controller gets a signal about the temperature. I've connected it to an innocent looking cable :-) On the other hand I can manually adjust the speed level of all fans together. It's a Supermicro board.

[aunola]

That's very interesting. Would you care to explain in more detail how this is all hooked up?
I get from the smiley there is something obvious you connected it to for the temp, but I am afraid I didn't quite catch on ...

The way I understood these fan controllers is that it can either be given an external signal, usually from some MB fan connector, or you turn a knob manually to set the common fan speed. So I am very curious to know how you got temperature in there.

Thanks for taking time helping me out.

[JBeilke]

The fan-controler is connected to one of the FAN-connectors on the motherboard.

You find some pictures on this channel.
https://t.me/wildkatze_cfd

[aunola]

Thank you very much! I got confused when you said nothing was directly connected to the board.