<< Solved >> Sapphire Vega 56 Pulse - fails to boot with power connected to dGPU

[pastrychef]

Hi folks, I'm back at the machine again for the evening. Using the Vega HDMI and the EFI attached to this post, I was able to get past the gIOScreenLockState 3 failure and boot to the Mojave installation screen. Then I wondered if this configuration would also allow me to boot into my existing Mojave installation, so I cancelled the fresh installation I was about to do and tried it - and it works.

While this is great, I need to get at least two of the Vega DisplayPorts working for this GPU to have a future with me Any ideas why the HDMI on the Vega is working, but not any of the three DP ports?

Which Vega are you using? On reference style cards, the DisplayPort next to the HDMI works without having to add/fix anything. Adding WhateverGreen enables the other two DisplayPorts.

Btw, in your config.plist > Devices > Properties, you don't need that stolenmem thing. It's only needed if you can not set the amount of RAM to allocate to the IGPU in BIOS.

 

[mcljot]

It's a Sapphire Radeon Vega 56 Pulse. This is the exact card and company I bought from.

Evidently, adding WhateverGreen isn't working for me - is there some customization of WhatevGreen I can do to tinker with the DisplayPorts?

I'll remove the stolenmem property, thanks.

Edit: The fans on the Vega aren't spinning at all in this otherwise-working configuration. I tried using VGTab to set the minimum speed to 800rpm, still nothing.

 

[mcljot]

Here's the system report. It's recognising the card, and also recognising that I have a monitor connected to DisplayPort.

 

[pastrychef]

It's a Sapphire Radeon Vega 56 Pulse. This is the exact card and company I bought from.

Evidently, adding WhateverGreen isn't working for me - is there some customization of WhatevGreen I can do to tinker with the DisplayPorts?

I'll remove the stolenmem property, thanks.

Edit: The fans on the Vega aren't spinning at all in this otherwise-working configuration. I tried using VGTab to set the minimum speed to 800rpm, still nothing.

Here's the system report. It's recognising the card, and also recognising that I have a monitor connected to DisplayPort.

View attachment 388572

It appears the card is fully recognized by macOS...

It's not a reference style card and VGTab isn't guaranteed to work with non-reference cards. It's likely that the firmware on the card keeps the fans off until the GPU heats up.

 

[mcljot]

Well, check this out! Left monitor works with all three DP ports. Right monitor does not work with DP ever, not with any of my DP cables, only with HDMI.

• Tested DP cable #1 with left monitor on all three Vega DP ports. Works perfectly, reboots without issue
• Tested DP cable #2 with left monitor on all three Vega DP ports. Works perfectly, reboots without issue
• Tested DP cable #1 with right monitor on all three Vega DP ports. No display.
• Tested DP cable #2 with right monitor on all three Vega DP ports. No display
• Tested HDMI cable with left monitor. Works perfectly, reboots without issue.
• Tested HDMI cable with right monitor. Works perfectly, reboots without issue.
• Tested both monitors with DP. Left monitor works, right monitor doesn't. Reboots without issue.
• Tested both monitors with DP cables switched. Left monitor works, right monitor doesn't. Reboots without issue.

This leads me to believe that the monitor is at fault. However, both monitors work perfectly (and simultaneously) with my 2015 MBP (using two ThunderBolt 2 to DisplayPort cables). Also, both monitors work daisy-chained with my ThinkPad P50, using a mini-DisplayPort to Displayport cable. Something doesn't add up.

For the here and now, however, I believe I don't have to return the Vega in the morning. So that's a big relief!

Had I been using the left monitor for all this testing over the past 10 days, I believe this would have been such a simple process. All of my other experience with different machines showed both monitors working perfectly, so I guess I couldn't have known.

 

[CaseySJ]

What is the make and model of the monitor (assuming both are same make and model)?

Does the monitor support MST (multi stream transport) and, if so, are the two monitors configured differently? I would compare all of the video and other settings between the two monitors to determine what is different with the right-side monitor.

Edit: Because your ThinkPad is daisychained, it implies MST.

 

[mcljot]

What is the make and model of the monitor (assuming both are same make and model)?

Does the monitor support MST (multi stream transport) and, if so, are the two monitors configured differently? I would compare all of the video and other settings between the two monitors to determine what is different with the right-side monitor.

Good call. Both monitors are Dell U2719D, both support MST, both are set to enable DisplayPort 1.2, and both are 5 weeks old. However - I just reset the right hand monitor to factory default anyway, and now it works!! Two DP monitors. Rebooting perfectly. This has been a bit of an odyssey over something so simple and stupid. Thank you all @CaseySJ @Pavo and @pastrychef for your help and encouragement!

 

[CaseySJ]

Awesome! You should mark this one [SOLVED] in the title of the thread!

Nevermind -- already marked as such...

 

[mcljot]

Awesome! You should mark this one [SOLVED] in the title of the thread!

Nevermind -- already marked as such...

Yep, someone beat me to it Thanks again Casey for a great build guide and an extra-stellar performance helping me out!

 

[CaseySJ]

Yep, someone beat me to it Thanks again Casey for a great build guide and an extra-stellar performance helping me out!

You're quite welcome! The performance of this system is really impressive -- an equivalent system from Apple would costs thousands more. As for the Vega fans, have you tried the Vega Fan and Crash solution (Method 2) from the build guide?