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cuppuccino

macrumors newbie
Original poster
Apr 6, 2020
15
1
Hello community,

first post here, hopefully in the right forum. I need help with a dual GPU issue.

[UPDATE: I resolve my problems, see: Comment]

I've been successfully running a flashed GTX 1080 from MacVidCards /w boot screen on High Sierra but absolutely need to update to Mojave+ for work reasons.

So I ordered a GT 710 with native Metal support and put it into my MacPro right in the top PCIe slot. Now here's the dilemma:

1) Running only the 1080 (with boot screen) boots into an unaccelerated Mojave, as expected due to missing drivers.

2) Running only the 710 (without boot screen) successfully boots into accelerated Mojave, yeah!

3) Running both cards (screen connected to the 710) the MacPro won't boot to macOS and I have to power off (which happens instantly when I press the button).

4) Running both cards (screen connected to the 1080 /w boot screen) I can boot to Mojave but the progress bar disappears after completing and the screen remains white/grey. Connecting a second screen to the 710 luckily reveals Mojave on the second screen. I just have to mirror the primary screen of the 1080 to get the login mask and can use Mojave this way.

5) Bootcamp partition also only seems to work with just the 1080, not with both, as the boot screen just gets stuck after I select the Windows partition. Using the Startup Disk setting the Mac does indeed attempt to boot into Windows, shows the Logo but then black screens and reboots into boot screen.

So it seems I can use Mojave with both cards but somehow the 1080 gets precedence (maybe due to flashing for boot screen?) and the 710 gets recognized as a separate screen which I have to abuse via mirroring.

Is there anything I can do to make this work properly without pluggin/unpluggin my cards? Like somehow setting that the 710 is the primary card when both are connected? Also Bootcamp would be great to work with both cards.

Best
 
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UPDATE:

I got everything working now. I have both cards plugged in and connected via HDMI to one screen.

As for macOS: When I'm booting I have boot screen from my 1080 and once Mojave is up the 1080 basically is idle with a white screen due to missing drivers so I change my screen to Input2 where the 710 is sitting and mirroring the 1080. (Be careful to mirror DISPLAY not your screen brand in the settings for full acceleration!).

As for Windows: I had to format my disk and reinstall Windows in EFI mode (!). Additionally I installed the iMacPro bootcamp software and now I can fully make use of the boot manager/startup disk and swap between both operating systems without problems. Also due to both cards plugged in, I recommend to disable the weaker card inside device manager.

Now I enjoy fully accelerated Mojave with the GT 710 and power house gaming inside Windows with the GTX 1080.

Best
 
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