Solved by 1440p HiDPI: MacBook Pro 16“ is HOT and NOISY with an external monitor

But if you force enable HiDPI mode for your external monitor, this is what happens:

Now the external monitor is treated as a HiDPI display

Now the GPU power draw is only around 5–6W.

What exactly is HiDPI mode? Well, it’s basically forcing macOS to internally render at 2x resolution. So in the case of a 2560x1440p monitor, macOS is internally rendering at 5120x2880p. You can tell, since the screenshot of the power draw monitoring utility (iStat Menus) is twice as sharp in the second example.

Now the MacBook is drawing a much more reasonable 5–6W and stays silent during normal operation, as it should! Now it feels like a Pro machine!

Seeing as how it makes no sense that rendering at 2x resolution cause 1/3 of the power draw, this is most likely a GPU driver bug on Apple or AMD’s end, and a temporary solution could be force enabling HiDPI mode for 1440p monitors in the next release of macOS Big Sur.

Note, these power draw settings only work if you keep the MacBook lid closed.

from Hacker News https://ift.tt/3wDMCFJ