kernel_task CPU usage with external display

Bibou37,

Thanks for your post! We see your usage will go up to 500% when using an external monitor. We see it also happened on your previous Mac. See if the issue persists in another user.

Set up users, guests, and groups on Mac

Are you able to test the issue with another monitor?

Let us know what you find out!

Take care!

Hi Bibou37

Thanks for the response. When you create the new user we suggest setting it up as an admin, then testing. If the issue persists in the new admin, we would then suggest reinstalling your macOS. Before reinstalling, we advise to create a backup.

Back up your Mac with Time Machine

How to reinstall macOS from macOS Recovery

Cheers!

Hi Bibou37,

Thanks for replying. If the issue persists you can try to restore from your Time Machine backup, but if the issue persists, you would want to try without restoring to see if the issue was related to a backup.

Restore your Mac from a backup

Best regards.

kernel_task CPU usage spikes up to over 500% means your 16" MBP is overheating. kernel_task is that high because it's trying to slow down your computer down (as fake CPU usage) so it's cooler as a last ditch effort to cool things down.

The 16" MBPs have huge issues with overheating when using an external monitor that Apple still hasn't fixed.

See this huge thread on the overheating 16" MBP with external monitor issue:

https://discussions.apple.com/thread/250878229

I'm having the same trouble and it appears to be related to the external monitors like you said! Did you find a solution?

I have been having this same issue ever since upgrading from Catalina 10.15.5 to 10.15.6 on my 2016 15" MBP. On Catalina 10.15.5 it worked perfectly fine. My issue, however, is a little more specific. It doesn't happen any time, only when I stream video via a web browser. Video via an application such as VLC works fine. At first I thought it was the web browser, but it happens with both Firefox as well as Chrome. I also validated that the web browsers were both on the latest release. I use two external monitors -- one is connected to a docking station, which connects to my computer via USB-C, and the other monitor uses a USB to DVI video adapter (which is then in turn plugged into the docking station). I didn't correlate this issue to the monitor at all until I read this post. After reading this post I tried removing the monitor that was using the USB video adapter, but the issue persisted. Then I unplugged the docking station and used only the laptop built-in display. When I did that I had no issues at all!

I don't completely buy this answer. I've had the same two external monitors for a while and they never had the problem when I was on High Sierra, nor did it have the issue after I upgraded to Catalina 10.15.5. It was not until I upgraded to 10.15.6 that the issue started happening. It's so bad that I almost can't use my external monitors, which is not really possible since I use them for photo editing.

It's a combination of Turbo Boost making CPU run for a short burst at incredible high speed and heating up everything, and Chrome, the most notorious RoadHog in existence, and your running Sophos so-called Anti-Virus resource sink.

Getting rid of Turbo Boost with Turbo Boost Switcher, using Firefox or Safari instead of that bloatware, and removing Sophos dreck from your Mac permanently will reduce the issue you reported dramatically.