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DamnTrain

macrumors newbie
Original poster
Mar 5, 2022
10
2
So now my Mac Pro 5,1 has been upgraded with an RX560 graphic card. Now there is an issue related to its HDMI output: When switching the signal away from Mac running macOS (10.14) to another source and then back on the monitor (e.g. Switching from the Mac on HDMI2 to the Xbox on HDMI1, then back to HDMI2), either the monitor can no longer pick up the signal from the Mac or the Mac shuts off the video signal. The monitor stays black as if the Mac is not turned on. And this could only be solved by either pulling out the HDMI cable from the Mac side and then connecting it back a few seconds later, or simply hard resetting the Mac. The Mac isn't halted though; everything is still running, the caps lock still responds, and the internal speaker still makes "bong" sound when performing invalid keyboard operations.

This problem doesn't happen when using DVI port or running Windows. Some Googling online revealed that this problem also plagues some users with other Mac computers such as Mac Mini/MacBook Pro, and the solution is to disable HDMI/DP hotplug detection on the monitor, which is an option that's not available on my monitor.

So I wonder, if the monitor or macOS itself cannot process hotplug events properly, is there a way to prevent macOS from receiving or processing these events?
 

mattspace

macrumors 68040
Jun 5, 2013
3,186
2,879
Australia
When switching the signal away from Mac running macOS (10.14) to another source and then back on the monitor (e.g. Switching from the Mac on HDMI2 to the Xbox on HDMI1, then back to HDMI2), either the monitor can no longer pick up the signal from the Mac or the Mac shuts off the video signal.

I wonder if having a display with PiP capability prevents this, as it has to keep the display signal live from multiple sources. I have my Mac on HDMI 1, and Xbox on HDMI 2 and switching the display back & forth is faultless.
 

Borowski

macrumors regular
Oct 22, 2018
215
50
Perhaps a EDID-simulator (detected as a dummy-display w/ fixed resolution) could solve the problem.
 

DamnTrain

macrumors newbie
Original poster
Mar 5, 2022
10
2
I think I might have found a solution by using Lilu+Whatevergreen and adding -igfxonln=1 to boot-args to force all video ports online.
 
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