[Solved] Three-screen setup, black screen (no signal detected) on TV via HDMI.

[Shanghaidaddy]

Yeah, HDMI works fine for me in Windows too. But once I try to boot in to macOS, I get problems. Same cable.

Do you use any injection or SSDT for your AMD graphic cards in your builds?

 

[pastrychef]

Do you use any injection or SSDT for your AMD graphic cards in your builds?

I'm currently using a kext to inject framebuffer properties. It seems to help with benchmark numbers. However, it works fine without the framebuffer properties injection too. I don't even use WhateverGreen anymore.

 

[Shanghaidaddy]

I'm currently using a kext to inject framebuffer properties. It seems to help with benchmark numbers. However, it works fine without the framebuffer properties injection too. I don't even use WhateverGreen anymore.

Interesting. I tried booting without (earlier version of) WhateverGreen once, and it showed black screen. I am sure it booted to macOS login screen since I can hear the Funk alert sound when I pressed the keyboard keys. Mind sharing what kext you are using? Curious to try.

 

[pastrychef]

Interesting. I tried booting without (earlier version of) WhateverGreen once, and it showed black screen. I am sure it booted to macOS login screen cause I hear the Funk alert sound when I pressed the keyboard keys. Mind sharing what kext you are using? Curious to try.

WhateverGreen helps enable all the video out ports on video cards. Without it, only two video out ports work on my Radeon VII and Vega 56. This is fine for me since I only have one monitor. You will have to do some trial-and-error testing to find which video out ports work without WhateverGreen.

 

[Shanghaidaddy]

Ahh. I read about it in this thread earlier today. Thanks for sharing. I'm going to try.

 

[mattystonnie]

Ahh. I read about it on this thread earlier today. Thanks for sharing. I'm going to try.

So the problem was the cable? Can you disable the hdr from tv and select a higher resolution?

 

[Shanghaidaddy]

So the problem was the cable? Can you disable the hdr from tv and select a higher resolution?

No, the cable is fine. Highest resolution on macOS is 3840 x 2160 with HDMI Ultra HD Deep Color on or off.

 

[pastrychef]

So the problem was the cable? Can you disable the hdr from tv and select a higher resolution?

HDMI in macOS has always been a problem for me. Sometimes, higher quality cables can help. But even with a very high quality cable, I can't get 100% stability with 4K@60Hz.

Lowering the refresh to 50Hz kind of works for me.
Lowering the refresh to 30Hz always works for me.

I have seen some people have success at getting stable 4K@60Hz using the Club-3D active HDMI 2.0 to DisplayPort adaptor but I have not tried this adaptor.

 

[Shanghaidaddy]

WhateverGreen helps enable all the video out ports on video cards. Without it, only two video out ports work on my Radeon VII and Vega 56. This is fine for me since I only have one monitor. You will have to do some trial-and-error testing to find which video out ports work without WhateverGreen.

Benchmark scores varies, with RadeonBoost.kext loaded, OpenCL score is 358 higher, while Metal score is 406 lower (See attached screenshots). I notice that more info is displayed in System Information - Graphics section too.

 

[Shanghaidaddy]

WhateverGreen helps enable all the video out ports on video cards. Without it, only two video out ports work on my Radeon VII and Vega 56. This is fine for me since I only have one monitor. You will have to do some trial-and-error testing to find which video out ports work without WhateverGreen.

With WhateverGreen disabled, all three screens were black after Apple boot logo, and purple lines were back too. I will stick with just WhateverGreen.kext for now since the injection didn't really help with my benchmark scores anyways.

Thanks again, man.