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External monitor revs kernel_task to 500%


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I have a MacBook Pro, 15 inch, 2016, using the LG 5K monitor that “replaced” the Apple Thunderbolt Display. Out of the blue it has started having the kernel_task run amok, over 500%, with the CPUs maxed out. But the temperature is virtually always the same, around 140 F. If I leave it alone the CPU and kernel_task calm down, but as soon as I start using it again it goes right back up and the computer becomes virtually unusable.

I’m on Big Sur, but this problem didn’t start when I updated, so I don’t think that’s the problem.

I accidentally discovered that if I ran the MBP without the external monitor it went back to normal (and no change in the temperatures, either). In googling for answers I’ve found many people with the same problem with other monitors as well, so it’s not just the LG. A lot of the proposed solutions revolve around the temperature, but that doesn’t seem to be the problem.

I sent it in to MacGeekGab and Dave suggested plugging the monitor in on the opposite side of the laptop, but that didn't help, so he suggested asking here ... any ideas out there? Thanks!

1 Answer

To me it sounds like it is using the Integrated intel graphics, and not the discrete GPU.


You could get gSwitch and see what GPU  is being used.

Thanks, that seems to have done the trick. I gladly donated in gratitude!