Hi I have a Macbook Pro (2019). Both my laptop and external monitor is getting slow frequently when i connect to a LG 4k external monitor. I am using typec to Hdmi adpater to connect to monitor.

My Laptop details: enter image description here

Also when this happens videos are getting pixelated (can be seen in the below image). enter image description here

All I can see is that my kernal_task is consuming too much cpu but not sure why this is happening. enter image description here

I have took some screenshots of temperatures from tg_pro app when this issue occurred, and it seems fine. enter image description here enter image description here

Any Idea, How I can fix the issue?

  • What else is connected to your system? The left ports on MBPs lead to more thermal throttling, although this seems not the issue here, I would try to (only) use the right ports, especially for anything power related. Further, that screenshot might indicate hardware failure. To rule out software you could do a clean install, but be sure to have a good backup. First though, I would also try to boot into safe mode, reset NVRAM/PRAM and SMC and check if that problem persists. Can you narrow down the issue to some activity or app that is causing this? Does this only happen with the monitor? – X_841 Mar 22 at 8:18
  • Yeah, this happens only with monitor – yellowspectre Mar 22 at 9:28

This looks like you have a faulty cable and I would look into replacing that immediately. The faulty cable is also causing the performance issues as kernel_task with such a high CPU usage means it is thermal throttling hard.

I've always used the Choetech brand for my USB-C to HDMI but PrimeCables will do as well. Make sure you're getting something rated for 4K 60Hz and check the reviews on whatever you intend to buy. As an aside, I'd look into a USB-C to DP adapter instead as this can result in a better experience with certain monitors.

  • I am using an official apple typec to hdmi adapter only – yellowspectre Mar 22 at 15:24
  • Can you test with another monitor? – X_841 Mar 22 at 17:32
  • currently i don't have another monitor. The setup was working fine when i connect another macbook pro using same cable. So i ruled out monitor and cable failure – yellowspectre Mar 24 at 6:49
  • I assume that you've tried NVRAM/PRAM resets? – LinuxLiaison Mar 24 at 19:13
  • yep, but resetting them doesn't resolve the issue – yellowspectre Mar 29 at 11:09

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