PCI Configuration Begin when plugged into second GPU, no video out when in macOS.

[HumerousGorgon]

Hello there,

I have a strange issue. Running a Xeon E5-2695v4 CPU on an Asus X99 Deluxe board with 2 Vega 64's plugged into PCI slot 2 and PCI slot 5. While this isn't necessarily the ideal slot configuration, all my other slots are full with other devices. When I have a display plugged into the topmost slot GPU, the system boots to macOS no problem and both GPUs are detected in System Information. When I go to plug in a monitor to the second GPU, I get a black screen. The monitor however does initialise and detect a HDR signal.

The interesting part is that when I'm plugged into only the second GPU and go to boot the system, I get stuck at PCI Configuration begin. The operating system will not post when I'm solely plugged into the second GPU.

While normally I would say that this is a motherboard issue... posting into Windows yields me a perfect boot with display out on either GPU or both GPUs. I'm not sure where to turn.

Happy to share any resources/info that you guys might need. Apart from this issue, I have a perfect working system. I just need my second GPU!

Thank you!

 

[P1LGRIM]

The operating system will not post

posting into Windows

You seem to be confused as to the meaning of POST.
It is an acronym for Power On Self Test and as the name suggests it is performed when power is applied to the system.
If the POST fails then the system halts, usually with some form of error code.

Thus no operating system 'posts', you cannot post into Windows.
Perhaps you mean boot ?

 

[HumerousGorgon]

You seem to be confused as to the meaning of POST.
It is an acronym for Power On Self Test and as the name suggests it is performed when power is applied to the system.
If the POST fails then the system halts, usually with some form of error code.

Thus no operating system 'posts', you cannot post into Windows.
Perhaps you mean boot ?

I do in this case mean boot, yes. The system boots to macOS when plugged into the first GPU, but will not progress past PCI Configuration begin when plugged into the second. It also will not give a video output when switching the cable into the second GPU after booting.

Windows boots and works as expected.