Ubuntu – In Ubuntu 20.10 cpu clock fixed at 800MHz

20.10cpuintelperformance

I'm running into a problem specifically with Ubuntu 20.10 and derivatives where the cpu clock is fixed at 800MHz for all cores.
This happens with a fresh install of Ubuntu, Kubuntu or POP_OS! 20.10.

However when I install Ubuntu 20.04 all works well- until I upgrade to 20.10. After upgrading the CPU is stuck again.

My laptop is a Dell Precision 7530, the CPU is i9-8950HK.
There is a thread (Ubuntu is very slow when Intel SpeedStep is enabled (CPU is not used in full speed)) that suggests a power adapter problem which causes the BIOS to limit CPU scaling. I can't find any evidence that this is the problem I'm experiencing- the file /sys/devices/system/cpu/cpu*/cpufreq/bios_limit does not exist on my system.

Here's the output for cpu0 on Ubuntu 20.10- compared to my current 20.04 system I did not see any differences, except of course a higher frequency:

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 4294.55 ms.
  hardware limits: 800 MHz - 4.80 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 4.80 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.

In addition I'd like to not that I dual boot this machine with Windows 10 on a different drive, and I didn't experience any problems with Windows performance. But maybe Windows sets some weird flags that cause these problems in Ubuntu?
During all my tests with Ubuntu I did not boot into Windows- in case that's important.

Do you have any advice how to further debug this problem and to get to the root of it?

Thanks!

Update 14.01.2021

I just found out the this clock speed issue does not occur in Ubuntu 21.04 beta, it is something specific to Ubuntu 20.10 and derivatives.
That does unfortunately not tell me what the exact problem is, but at least it shows me a working path forward waiting on the next release.

Best Answer

I think this will probably be solved by removing thermald.

See also here: https://www.reddit.com/r/archlinux/comments/b66d3k/why_was_thermald_removed_from_the_repos/ In that thread someone also mentions a PC being stuck at low frequency because of thermald.

I downgraded to ubuntu 20.04 because of this problem, but recently (perhaps after a thermald upgrade, or a kernel upgrade), I got into new problems: now my PC shuts itself off on heavy load. So after some more research, I decided that it was safe to remove thermald and that problem is now solved.

I don't feel like trying to upgrade to ubuntu 20.10 again, but anyone stumbling on this problem could give removing thermald a try.

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