[SOLVED] Vega 56, DisplayPorts not working, HDMIs do

[erikstr]

Hi guys
I am having a hard time finding out the cause of this problem. I have a Sapphire Nitro+ Radeon RX Vega 56 card with 2x DisplayPort and 2x HDMI ports, which is actually working with High Sierra except that there is no signal at the DisplayPort ports. Attached are all problem reporting files. Please someone make a suggestion which of my settings might be wrong. Thanks in advance!

 

[qbe]

install lilu and whatevergreen kext (or vegafixup.kext instead of whatevergreen)

 

[erikstr]

Thank you so much! Lilu.kext+VegaGraphicsFixup.kext fixed the problem!

 

[wlein]

I'm having the exact same problem with my Vega 64; 10.13.5, iMacPro1,1. Everything works great except for the DP ports.

I tried VegaGraphicsFixup, Whatevergreen, and 20+ different configs and nothing.

Does anyone have any idea how to fix this issue?

 

[P1LGRIM]

Does anyone have any idea how to fix this issue?

Try your iMacPro1,1 SMBIOS but with an iMac14,2 Board-ID (Mac-27ADBB7B4CEE8E61).
I saw someone post this fix for Nvidia graphics but who knows ?

 

[wlein]

Thanks for the super prompt reply.

Unfortunately, no dice.

I noticed that turning off DisplayPort 1.2 in my monitor settings fixes the issue but I'm limited at 30Hz which makes it pretty useless.

 

[erikstr]

Thanks for the super prompt reply.

Unfortunately, no dice.

I noticed that turning off DisplayPort 1.2 in my monitor settings fixes the issue but I'm limited at 30Hz which makes it pretty useless.

Plug in a TV or a second monitor to one of the HDMI ports together with the main monitor over DP. Then boot - only the HDMI will come up. Then play with un/plugging both cables until the DP comes up. Then unplug the HDMI, configure the DP Monitor and reboot - now the DP monitor will come up first. I think the Vegas have some kind of memory where they notice which port should be first. I am not sure what exactly happens but it works

 

[wlein]

For posterity: the issue is fixed.

I switched my DP cable (2.5m) with a shorter one (2m) and it just worked.