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My 2015 i7 MacBookPro started to thermal throttle after the update to Big Sur:

  • in previous system, the Mac went up to 90°C degrees before slowing down. And it would not thermal throttle at all. The thermal throttling temperature seemed to be 98°C degrees.
  • currently it thermal throttles at 70°C degrees: the CPU frequency slows down to 800 MHz and GPU down to 200 MHz (as indicated by Intel Power Gadget)

This is all after I installed "Macs Fan Control" and this is after I set it to "Full Blast" which means 6100 RPM. I have already changed the CPU thermal paste.

How can I change the "thermal throttling" temperature to a higher value?

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The "problem" will most likely disappear if you turn off MacsFan Control.

I have experienced very similar problems when settings MacsFan Control to full blast thinking, this would ensure the coolest CPU temps possible. However, in my case kernel_task started to spike to a couple 100% of CPU usage which is very often an indicator for thermal throttling.

My suspicion is that when setting the fan speed with MacsFan Control your MacBook loses control over the fan speed and as it does not know what you will do next it starts throttling to avoid any problems.

When your MacBook controls the FanSpeed it knows it can adjust the fan speed and CPU/GPU power as needed, however, when you manually set the fan speed it loses part of its mechanism to ensure low enough temps for the Computer. It then plays it safe by throttling the CPU so much that it will definitely not be harmful in case you would e.g. suddenly completely turn off the fans.

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  • Thanks I will try. Log ago Macs Fan Control was "necessary" because Mac firmware preferred thermal throttling and staying quiet to blasting the fan. But I re-try that. This is a new system after all.
    – user418915
    Jul 8, 2021 at 22:31
  • Turning off Macs Fan Control does not work: computer still maintains 70C by aggressively trottling the CPU and GPU.
    – user418915
    Jul 17, 2021 at 20:14
  • Could you revert to Catalina and check if its actually the update that made things worse?
    – X_841
    Jul 18, 2021 at 7:01
  • I am pretty sure this is the case. I did not have Macs Fan Controls, and I remember that CPU did go over 80C several times only then I would run the MFC. I did not have it "always on". As for revert, it requires a Time Machine backup of a Catalina system. The Time machine did delete all old backups after it claimed the data was corrupted (it does it once every few months), and all backups I have are of Big Sur. I will try SMC reset and things like that.
    – user418915
    Jul 19, 2021 at 8:25
  • After the computer was restarted I am getting 99C now under load. I turned on Macs Fan Control, and it is still 99C (the fans were already at max). After the video was encoded, I kept MFC on "full blast", the cpu temperature dropped down to 65C, when another video was transcoded the CPU went up to the 99C back again. So my "problem" disappeared. But it has existed for some time. It seems the trigger is something else than MFC, but it is cleared by a machine restart. I will try to guess what causes it.
    – user418915
    Jul 20, 2021 at 14:57

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