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I have a system running Ubuntu 22.04.3 LTS (GNU/Linux 5.15.0-82-generic x86_64).

I started noticing that it sits around 3.4 GHz like it should but when it goes under load, all cores drop to 800MHz.

I first thought it must be a temperature issue but all cores are at under 35C. Shouldn't be a power issue either as at 3.4GHz it shouldn't draw more than 65W.

After looking at the forums, a lot of the threads lead to this command "wrmsr 0x1FC 2". When I run it the cpu gets locked at 3.7GHz then becomes unresponsive after about 30 seconds.

Specs: Intel i7 6700 (non K) 32GB 2400mhz DDR4 Ram. 2x 1060 6G And a bunch of disks

Spillebulle
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  • Take a look at a similar question I asked. It may not be the same question or same solution but the post has some useful commands for seeing what your CPU is doing and looking at hardware flags that can cause throttling etc: https://askubuntu.com/questions/1446577/ – codlord Sep 03 '23 at 10:30
  • I wouldn't rule out power as not being the issue until you have all the power checked to be sure. Even though a CPU doesn't draw more than 65W doesn't mean that the power supply isn't supplying the 65W needed watts to the system. Also, depending on how many drives you have, the motherboard, the two video cards (which can draw up to 120W per card) installed into your system and how big your power supply is you may be overdrawing your power supply. – Terrance Sep 03 '23 at 14:59
  • @Terrance In the test I've been doing the GPU's have been at 0% usage. The powersupply is a 1000W powersupply from silverstone so it would be weird if that was the issue. There is no issue when the GPU's are under load and I don't know how that would explain the cpu being stuck at 800MHz – Spillebulle Sep 03 '23 at 15:22
  • @codlord I looked at the link you sent and it was very informative. I have pasted the output from one of the cores below, all the other cores show the same. I have set all cores to performance before with "sudo cpufreq-set -r -g performance" but since it says "powersave may decide which speed to use" does that mean powersave is in use instead of performance?

    https://pastebin.com/raw/PpwjKP5S

    I don't know how to check if the "Prochot flag" is enabled. How do I check and/or fix that?

     – Spillebulle Sep 03 '23 at 15:27
  • "when it goes under load, all cores drop to 800MHz." which is a power draw. I'm not saying that power is the issue, but just not to rule it out. It could very easily be a power saving mode turned on for the CPU, but that part is strange as to why all cores would drop to 800Mhz when the system is under load. Just one example I had recently, my file server kept crashing under load and sometimes wouldn't boot up, mostly after running under load. Turned out that the capacitors around the CPU socket had popped their tops and weren't supplying proper power to my CPU. – Terrance Sep 03 '23 at 16:36
  • @Spillebulle Output the results of the turbostat command from my linked post. It outputs a load of info then outputs CPU info every 5 seconds. In my case in the post you can see the lines with _LIMIT_REASONS and one which says (Active: PROCHOT, ). See if you have any active limit reasons when it's at 800MHz – codlord Sep 03 '23 at 16:44
  • @codlord I ran it at the same time as "stress" so it would be pinned at 800MHz on all cores

    https://pastebin.com/raw/v9mbB1ws

     – Spillebulle Sep 04 '23 at 05:16

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