Problems with HDMI output on AMD Sapphire Vega 56

[gcc1]

On my set up I am running a VEGA 56 dGPU with the Intel UHD 630 iGPU in headless mode using SMBIOS 19.1 and with the Display Port, it works faultlessly.

For various reasons, I'd like to use the HDMI output from the VEGA but when I do so, the display continually flickers on and off. I seem to remember reading that macOS has some issues with HDMI and was wondering if anyone knows of a solution to this. I have attached my config.plist.

Thanks.

 

[jaymonkey]

I'd like to use the HDMI output from the VEGA but when I do so, the display continually flickers on and off. I seem to remember reading that macOS has some issues with HDMI and was wondering if anyone knows of a solution to this. I have attached my config.plist.

@gcc1,

HDMI should work fine on Vega 56 ...
Have you installed the latest versions of Lilu + WhatEverGreen ? .. see this guide for more info :-

An iDiot's Guide To Lilu and its Plug-ins

An iDiot's Guide To Lilu and its Plug-in's Last Update: 22nd Jan 2021 (Add note about OpenCore config.plist modifications) About this Guide Note: This guide was written when Clover was the boot loader of choice as such the config.plist examples in this guide are mostley Clover specific ... if...

www.tonymacx86.com

After installing check which AMD frame buffer is in use by looking in the IOREG under the GFX0 device path ..

Cheers
jay

 

[gcc1]

@gcc1,

HDMI should work fine on Vega 56 ...
Have you installed the latest versions of Lilu + WhatEverGreen ? .. see this guide for more info :-

An iDiot's Guide To Lilu and its Plug-ins

An iDiot's Guide To Lilu and its Plug-in's Last Update: 22nd Jan 2021 (Add note about OpenCore config.plist modifications) About this Guide Note: This guide was written when Clover was the boot loader of choice as such the config.plist examples in this guide are mostley Clover specific ... if...

www.tonymacx86.com

After installing check which AMD frame buffer is in use by looking in the IOREG under the GFX0 device path ..

Cheers
jay

Thanks for the lightening fast response Jay.

Latest versions of both Whatevergreen and Lilu installed in L/E.

At GFX0 in IOREG showing 2 display device types with AMD Framebuffers (only using one display).

Have attached IOREG if it helps.

Thanks again!

 

[jaymonkey]

At GFX0 in IOREG showing 2 display device types with AMD Framebuffers (only using one display).

@gcc1,

IOREG shows that WEG has assigned AMD framebuffer correctly ... looks ok to me.
Have you tried using a different HDMI cable ?

Cheers
Jay

 

[gcc1]

@gcc1,

IOREG shows that WEG has assigned AMD framebuffer correctly ... looks ok to me.
Have you tried using a different HDMI cable ?

Cheers
Jay

I had been thinking that might be a possibility.

Will give it a go. Really appreciate your help and quick responses.

All the best!

 

[pastrychef]

I had been thinking that might be a possibility.

Will give it a go. Really appreciate your help and quick responses.

All the best!

In my experience, HDMI cables can make a difference. However, even with a good quality HDMI cable, it can be a bit glitchy when trying to use 4K@60Hz. If I use a lower resolution and/or lower refresh, it's more stable. YMMV.

This glitchiness only happens in macOS. On Windows, 4K@60Hz over HDMI works fine...

 

[gcc1]

In my experience, HDMI cables can make a difference. However, even with a good quality HDMI cable, it can be a bit glitchy when trying to use 4K@60Hz. If I use a lower resolution and/or lower refresh, it's more stable. YMMV.

This glitchiness only happens in macOS. On Windows, 4K@60Hz over HDMI works fine...

Thanks, that is also my experience with Windows when dual booting.

I'll try another cable and report back if there's an improvement.