SuperMicro & low-RPM fans

Stereodude

Active Member
Feb 21, 2016
412
65
28
USA
Are you saying that the motherboard is simply going to continue increasing fan speed based on temp with no care of RPM / tricked RPM?
That's how every enthusiast board I've seen does it. It drives PWM duty against temperature with no concern for fan RPM. You can usually control the curve in the BIOS. You get like 5 or so adjustment points where you can specify the minimum idle duty (regardless of how cold the CPU is, a few points linking a certain duty to a certain temp, and then a temp at which it should run 100%. A few I've seen will let you enable a minimum fan RPM warning and set that RPM if you want.

Even the Intel Server board I have doesn't run closed loop feedback on RPM. It differs from an enthusiast board and uses a closed loop system, but it's temperature based. It will simply ramp the fan's duty to whatever is necessary for a given cooling domain to maintain a programmed thermal margin. I "hacked" the .SDR file for my Intel board to make it hold a lot more thermal margin since I didn't think ~80C was a good operating temp for my CPUs when fully loaded. The Intel .SDR does define some characteristics for the fans, which include min and max RPM, so I guess if you changed the fans or faked the fan RPM on the Intel board it could detect a fault if the RPM went outside the expected range, but I don't see how the Supermicro board could have a similar mechanism.

Regardless, I can always change the RPM scaling factor being applied to the fans or make the factor non linear based on the fan RPM if I need to further outsmart Supermicro's inflexible fan control. It's a microcontroller running software and I can program it to do anything I want (as long as the code fits in the flash). Multiples of 2 are just really easy because you simply do a bitwise shift of the measured value to scale it.
 
  • Like
Reactions: cement_head

Stereodude

Active Member
Feb 21, 2016
412
65
28
USA
Seems Supermicro has set a hard lower RPM limit too:

Super Micro Computer, Inc. - FAQ Entry
Well that's certainly not true. I have an X9SRA and it goes full power way before 300RPM. Seems to be around 800-900RPM.

If it behaved that way I wouldn't have any complaints.

Edit: It's 700RPM. I sent Supermicro an email with a link to their FAQ, pointed out I had an X9 board and asked how I can get the performance they advertise. One of the Linux tools on the Ultimate Boot CD clearly shows they have a limit of 700RPM when it does a sensor scan. Watching a bit closer in the BIOS on the screen showing the fan RPM confirms that 700 is the magic number.

I probably won't get my parts from Digikey for a few days, so I can fume a bit longer.
 
Last edited:

Fritz

Well-Known Member
Apr 6, 2015
2,135
497
83
66
I'm trying to set the lower threshold using ipmitool but It's telling me it can't find the fan sensors. This is on a X9DRD-7LN4F-JBOD.

Any ideas? :(
 

pLu

New Member
Nov 25, 2015
19
4
3
Stockholm, Sweden
I'm trying to set the lower threshold using ipmitool but It's telling me it can't find the fan sensors. This is on a X9DRD-7LN4F-JBOD.

Any ideas? :(
Try for a list of sensors
ipmitool -I lanplus -H <ipmi host> -U <user> -P <password> sensor
or
ipmitool sensor
 

rubylaser

Active Member
Jan 4, 2013
842
229
43
Michigan, USA
Or this for a more condensed version with just the FAN values.
Code:
ipmitool -I lanplus -U Admin -H <ipaddress> sensor | grep FAN
It should give you output like this...
Code:
root@fileserver:~# ipmitool -I lanplus -U Admin -H 192.168.172.6 sensor | grep FAN
Password:
FAN 1            | na         |            | na    | 75.000    | 150.000   | 225.000   | 18975.000 | 19050.000 | 19125.000
FAN 2            | na         |            | na    | 75.000    | 150.000   | 225.000   | 18975.000 | 19050.000 | 19125.000
FAN 3            | na         |            | na    | 75.000    | 150.000   | 225.000   | 18975.000 | 19050.000 | 19125.000
FAN 4            | na         |            | na    | 75.000    | 150.000   | 225.000   | 18975.000 | 19050.000 | 19125.000
FAN A            | na         |            | na    | na        | na        | na        | na        | na        | na
 
  • Like
Reactions: T_Minus

pLu

New Member
Nov 25, 2015
19
4
3
Stockholm, Sweden
Well that's certainly not true. I have an X9SRA and it goes full power way before 300RPM. Seems to be around 800-900RPM.
I think it's a lower hard limit no matter what the limit is set to via the BMC.


One of the Linux tools on the Ultimate Boot CD clearly shows they have a limit of 700RPM when it does a sensor scan. Watching a bit closer in the BIOS on the screen showing the fan RPM confirms that 700 is the magic number.
I wonder if it's possible to change the limits in NVRAM without a BMC...
 

pLu

New Member
Nov 25, 2015
19
4
3
Stockholm, Sweden
I'm trying to set the lower threshold using ipmitool but It's telling me it can't find the fan sensors. This is on a X9DRD-7LN4F-JBOD.

Any ideas? :(
I just noticed that my X9 mb names the fans with a space ("FAN 1") while my X10 doesn't ("FAN1").
 
Last edited:

Stereodude

Active Member
Feb 21, 2016
412
65
28
USA
Still I will be curious to see what Supermicro says in reply to my e-mail, if anything.
Supermicro replied and asked me for a few more details about the fans I was using asked me to test with just the CPU fan. I gave them the test results and the fans' details. Supposedly they are going to check with their BIOS team and get back to me.
 

Stereodude

Active Member
Feb 21, 2016
412
65
28
USA
Why Lord, why? Why does this have to be so difficult? :(
It's the Linux way. It keeps the unwashed masses from using their superior OS.

Oh yeah... It also keeps Microsoft in control at a time where they're doing everything they can to alienate their user base.
 
  • Like
Reactions: Fritz