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I'm currently struggling with kernel task on my 1 year old Macbook Pro 16" 2019. Basically I'm currently using an external monitor which is connected to my macbook via a usbc to displayport cable which is connected to the right side of my macbook along side with the DC cable. On the left side I only have a dongle which I use to connect my mouse to my macbook.

Here are a couple of pictures showing my temperatures. I'd like to highlight the fact that I'm not running ANY task on my macbook. I just connected the external monitor.

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What I did so far in order to try to mitigate the issue:

  • Resetting the SMC
  • According to some people, kernel_task is triggered by "thunderbolt left proximity" temperature, but it doesnt seem to be my case. I tried completely disconnecting the dongle, the temperature reaches ~38 degrees, yet the issue persists
  • Completely wiped my mac to make sure the issue wasnt one of the softwares I had installed, but the issue persists even with almost no programs running in the background
  • Tried different monitors and cables. I tried using HDMI cables and my old BENQ monitor and my television, the issue still persists.
  • I tried using my macbook in clamshell mode and I bought a vertical laptop stand because according to some people it helps dissipating heat, but of course it wont work.

I know kernel_task is supposed to make the CPU less available to those processes which are causing the macbook to overheat, but why is it taking so much CPU when there's literally no user processes using the CPU and the macbook is not even hot?

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  • I have but none of that helped. I forgot to mention that my room's temperature is around 23 degrees which shouldnt be "too hot" for my macbook. Regardless of that I also have a fan on my desk to keep me and the macbook cooler but it just doesnt help.
    – Beter
    Jun 30 at 15:08
  • All your CPU cores are up towards 60°. That's enough for the Mac to be trying to cool itself. Completely different type of Mac, but mine is currently about 50° CPU, in a room at 25°. Fans are at nominal.
    – Tetsujin
    Jun 30 at 15:10
  • I agree but it's not even close to overheating. Are you using an external monitor too? If I disconnect the monitor the temperature drops to 38-40 degrees and I can run heavy tasks without kernel_task popping up. It just looks like my macbook struggles to handle external monitors.
    – Beter
    Jun 30 at 15:16
  • I always run 2x 27" 2k screens, but mine's a Mac Pro, not a laptop. Laptops are often mentioned as heating up when they have to drive a second screen.
    – Tetsujin
    Jun 30 at 15:19
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I finally fixed it!

After trying 3 different display port cables and 2 hdmi cables, I decided to buy another one from Amazon (it's the highest quality cable I could find. The other ones were very high quality too but apparently not enough)

The cable I bought is made by CABLEDECONN and it's a thunderbolt 3 to DisplayPort cable. It should be available on amazon for both europe and US.

In order to fix the issue though I also had to lower my refresh rate from 144hz to 120hz (this change made no difference with old cables). As soon as I did that, the GPU power usage dropped from 18W to 6W and now my mac idles at 56-57 degrees while in clamshell mode but with fans running at around 2000 rpm (compared to the previous 5000+ rpm). If I also use my macbook's monitor, the GPU power usage ramps back up to 18W but temperatures remain under control and fans run at ~3600-4000 rpm.

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