PWM Fan swap (Full Build)

So, Today I got around to swapping out the 6 case fans with Noctua NFP-12 redux-1700 PWM fans. I also installed a Noctua NH-D9 DX-3647 4U cooler on the CPU.

During post, they were super quiet, but once the system was fully up, they’d cycle from almost off to full blast every few seconds. In the IPMI under ‘Configuration’>‘Fan Mode’, I had set the fans to ‘Standard Speed’.

The issue stopped if I chose ‘Full Speed’, but they were running full out and not silent.

If I chose ‘Optimal Speed’, they would cycle.

The error log shows ‘lower critical’ and ‘lower non-recoverable’ errors.

From what I can find out, it appears the Noctua fans can spin lower than what supermicro expects. It then spins up the fans, releases control and the process starts over.

It looks like Jeff Geerling had previously dealt with this issue on a different Supermicro board:

Since my goal is a quiet server, I’ll try this next.


Best of luck!

Keep us updated.

I want to replace mine for quieter ones if possible.

Did you disconnect everything from the built-in fan board then? Everything straight into the mobo?

@c1rcaa ,
Yes all 6 case fans disconnected. all 6 replacement Noctua’s are straight to the motherboard (FAN2-5, FAN A, FAN B) The Noctua CPU fan is a dual PWM fan combo into a splitter at CPU1.

I think FAN A-C are supposed to be a different zone than FAN 1-5, so maybe a different profile can be loaded later, but for now I just need to slow them down and have them quieter.

For now, I’m looking to set values using ipmitool and a script to run at startup.

Mine did that too but settled down after restarting the BMC.

@Labrat , What profile did you set your fans too? Standard or optimal?

I believe it is at optimal. Mine are Arctic P12 and can’t hear them at all at the speed they are set at. Drive temps in the 30s.

@Labrat ,
Thanks for the info. It’s interesting that the Artic P12 have a lower low RPM (300RPM) than the Noctua NFP-12 redux (450RPM), yet you didn’t have any issues. Even after restarting the BMC, I would still get surges in either standard or optimal mode.

I think I have it solved and will post that next.

I think what’s happening is your BMC is expecting higher fan speeds and when your fans dip below the threshold(s), it spins them up to max to recover. I experienced the same when I swapped from the 8k RPM fans to Noctuas. I used IPMI commands to adjust the lower thresholds to avoid that cycle: Decrease Supermicro IPMI Fan Threshold

Edit: Jeff’s command is exactly what you need!



Problem: Stock fans and noise levels. This full build isn’t going to run in a server rack (yet). The noise levels were too loud and were running full tilt.

I swapped out stock fans for 6 PWM fans and added cpu cooler with 2 fans ( see specifics in 1st post). Upon reboot, either standard or optimal mode would result in fans spinning up to full blast and then cycling down. Repeat every few seconds.

My homelab is in disarray (shocking). I couldn’t get ipmitool installed on rocky and I didn’t want to fight the repo battle yet, but I do have Ubuntu for Windows 10 subsystem on Linux installed, so I ran:
sudo apt-get install ipmitool

I was able to run: ipmitool -I lanplus -H “IP Address” -U “USERNAME” -P “PASSWORD” sensor get FAN2
this told me my preset values for:
Lower Non Recoverable - 300 RPM
Lower Critical - 500 RPM
Lower Non Critical - 700 RPM

So, basically, when my Noctua fans ran at their normal speeds, they would be below some of these values and the system would spin them up. Once the RPM’s were high enough, the system would release them and they would go back to the previous level (which were to low) and repeat. The warnings were in my system logs.

My solution was pulled from the “Fan Surge Correction” section of: New Home Lab – Paul Fitzgerald
I set Fans 1-5 as well as FanA and FanB to the following ( I did not change any of the High values):
Lower Non Recoverable - 100 RPM
Lower Critical - 200 RPM
Lower Non Critical - 300 RPM.

Then I restarted the BMC only. Now under both standard and optimal my cpu fan is at 600rpm and my 6 PWM fans are at 300rpm.

I have not added this as a startup script to set these values.

Now, time to catch up to @rymandle05 and start testing used SAS drives (HGST HUH728080AL4200)


Godspeed my friend! Glad to hear I’m not alone on the used SAS drive train. :grin:

Yep, standard w/ Supermicro boards. The ‘stock’ fans are powered off the PSU direct, so it’s not an issue. If you connect to the board headers, it will expect a minimum RPM and a lot of consumer (non-DC) fans spin too low.

Here’s some more info:

Mine are set to Standard, which start off around 500RPM, which is Low-Critical and will cause alarms in the BMC, but won’t spin them up/down. After the system runs for a little while and has had a chance to get warm, they’ll bump up to 600-700RPM and the critical alerts will clear.

Mine are all Noctua NF-P12 redux-1700 PWM.

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