Three days ago I started noticing my CPU fan loudly winding up and down when idling (with which I mean not running any particular program). I checked the CPU temperature which was and still is fluctuating between 50°C and 60°C. I also have Windows 10 installed as a dual boot where the CPU temperature readings still are about 40°C and the fans are quiet.

I am using Ubuntu 20.04 now for about two months and was observing the temperatures of my GPU and CPU with the gnome-extension Freon from the beginning. The GPU temperature always hovered around 38°C while the CPU was a couple of degrees below that. The GPU temperature is still uneffected so far.

First, I thought the sensor readings might be wrong, which lead me to the sensors-detect command. Running changed nothing though.
I also checked the BIOS where I could also see temperature readings for the CPU and adjust fan curves. The temperature was similarly high around 55°C, though I have read that this can be due to the BIOS just using a lot of CPU load.
Then I checked the CPU load when idling in Ubuntu with top and the built-in System Monitor. All processes in System Monitor had CPU usages of 0 or sometimes 1 which is strange. Top seems to show more sensible data, though even there the total CPU usage does not seem to exceed 20%.
Lastly I adjusted the BIOS fancurve for the CPU fan to the minimum frequency that it allowed. The temperature readings in Ubuntu were not noticeably influenced by this. The readings still fluctuate between 50 and 60°C, still regularly making 10°C jumps up and down.

My Hardware is
CPU: AMD Ryzen 7 3800X 8-Core Processor
GPU: Nvidia GeForce RTX 2070 SUPER

What else could I investigate? What could cause this?

  • 1
    What type of cooler is on the CPU? 55C sounds normal for a stock cooler, a nicer one should get you down in the 30C range when idle. You didn't mention the Windows CPU temps. Is fancontrol being used to control the fan?
    – rtaft
    Jan 5, 2022 at 18:57
  • 1
    The CPU uses the stock cooler. The Windows CPU temperatures are around 40°C, the fans often times don't even spin up. I do not use fancontrol and as far as I have tested can't even use it. sensors-detect does not find any modules which fancontrol can control.
    – Fantos
    Jan 5, 2022 at 19:26
  • Absolutely fine temps. Install thermald if it's not already installed. If your CPU or RAM are overclocked, that might explain it. Same with Nvidia 2070.
    – heynnema
    Jan 5, 2022 at 19:42
  • @heynnema Thank you for the suggestion, I will look into thermald. It still leaves the question of what has changed from four days ago though. I do not (actively) overclock my CPU or RAM. I also have not stress tested the CPU yet to see whether I get into thermal throttling territory then.
    – Fantos
    Jan 5, 2022 at 19:57
  • A variation between 40⁰ - 60⁰ C is a non-issue in my opinion. These are perfectly normal and safe operating temperatures and not "high" in any metric. It sounds like there are just different thresholds for when your cooler ramps up. thermald is a good suggestion.
    – Nmath
    Jan 5, 2022 at 22:09

1 Answer 1


Ubuntu 21.10 on a Librem 15, While working, i get all CPU's at 100%, fan on all the time... Just installed cpupower-gui and reduced the MaxFreq of all CPU's like so:

enter image description here

As far as i can tell, no major issues with performance, and for the same workload as before, CPU's now set to less than 60%.

Not sure if it helps.

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