Intel S2600CP2J - tweak SDR for 100% PWM at all times?

[5mall5nail5]

Hey guys - so, what if you wanted to tweak the SDR for 100% PWM at all times? Or, perhaps limit the fans to 60-100% so that the fan speed doesn't fall very low?

I am using Noctua NH-U9DXi4 with 92mm fans (NF-B9-1600 RPM PWM). These fans are not very high speed to begin with so I'd like to maybe keep it from spinning less than 1000 RPM at any time. Any thoughts? Thanks!

 

[psylenced]

There is a setting in the bios that lets you bump up the fan speed - have you looked into that?

Can't think of the name off the top of my head, but I believe it's on the same screen and nearby to the fan performance setting.

 

[5mall5nail5]

You're right its the PWM Offset. I put it at 60 which I guess would be 60%, and the fan speed is max. I am OK with that for my purposes.

Thanks!

 

[i386]

You're right its the PWM Offset. I put it at 60 which I guess would be 60%, and the fan speed is max. I am OK with that for my purposes.

Thanks!

I think the pwm offsets are in hex, a pwm offset with 60 would be 96% of max speed.

 

[5mall5nail5]

I think the pwm offsets are in hex, a pwm offset with 60 would be 96% of max speed.

Ha - wow. That's not clear. I'll experiment. My base RPM prior was about 680 RPM. Putting 60 or 65 in that field results in 1568 RPM... which is not what i'd expect 60-65% to be (fans are 1600 RPM @ 100%).

 

[5mall5nail5]

Well, not entirely sure it's in hex but the PWM offset in the BIOS does raise or lower the fan speed. I had "60" in there which would suggest that the speed was "96%". However, I changed it to "32" without changing CPU load (idling) which is "50" in decimal and yet the fan speed went from 1580 or so to 1176 RPM. Not quite "50% of "96%", but obviously lower. I'll deal with it I suppose just wish we knew what that did exactly.

 

[psylenced]

From the manual:

This feature is reserved for manual adjustment to the minimum fan speed curves. The valid
range is from [0 to 100] which stands for 0% to 100% PWM adding to the minimum fan speed.
This feature is valid when Quiet Fan Idle Mode is at Enabled state. The default setting is [0].

 

[5mall5nail5]

Yeah makes more sense - so I am adding 50% PWM over the baseline, whatever that is. So if my lowest speed has been 686 RPM @ X% this is 1300 RPM @ X% + 50%

 

[wildpig1234]

is your cpu temperature that high at idle and during sustained stress? there is that quiet idle fan setting which means that the fan speed can go to idle so it might mean that its not unusual that the whole thing would usually run fan at low speed anyway. i would defintely check the temperature behavior first so then you can know the ballpark of how much more fan speed you need.

 

[5mall5nail5]

is your cpu temperature that high at idle and during sustained stress? there is that quiet idle fan setting which means that the fan speed can go to idle so it might mean that its not unusual that the whole thing would usually run fan at low speed anyway. i would defintely check the temperature behavior first so then you can know the ballpark of how much more fan speed you need.

This is a very high-demand ESXi host. So for instance, just today, I built a colleague a 32 vCPU 16GB VM for running john the ripper on some things for our job(s). In doing so, the overall host CPU load will go from maybe 3 - 5% to 100% on all cores in a matter of seconds and run for maybe 1 hour, and come back down. So, rather than ramp up from 600 RPM, I'd rather just run the server with the fans at 1100-1200 RPM (the Noctuas are so quiet anyway), and ramp from 1200 RPM to 1600 RPM as needed. It means that the server can keep temps in check from the start of the workload.