My RX 5700XT eGPU vs the Radeon Pro Vega $$ inside a 2020 Mac Pro
Software: Blender 2.81 for Mac OS + AMD Radeon Pro Render for Mac OS (Metal)
Test: GPU-only render of the BMW Scene (at 640 samples) using Metal
Mac Pro 2020 and internal AMD RX 5700XT: 40 seconds (per Barefeats)
Mac Pro 2020 and internal AMD Radeon Pro Vega II: 41 seconds (per Barefeats)
My Mac Mini 2018 and PowerColor RX 5700XT in PowerColor Gaming Station: 44 seconds
The MPX module has its advantages over the standard PCIe graphics cards. Performance is not one of them.
It would be very cool if third-party vendors can work on an extension adapter to turn PCIe GPUs into MPX-compatible.
The MPX adapter would have:
2 x PCIe 3.0 x4 slots (to connect two Thunderbolt 3 add-in cards) or 2 x Titan Ridge Thunderbolt 3 controllers.
4 x mini DisplayPort 1.4 inputs (or 8 if the adapter has two Titan Ridge Thunderbolt 3 controllers).
2 x USB 2.0 9 pin headers (for Thunderbolt 3 add-in card or direct connect to two Titan Ridge Thunderbolt 3 controllers).
2+ PCIe 8 pin power connectors (optional).
You would install one per MPX slot (two total).
How much room is there between the top of a non-MPX GPU and the outer case of the Mac Pro 2019? That's where I would put the connectors so you can still insert 4 GPUs.
The PCIe 3.0 x4 slots can be populated with GC-TITAN RIDGE cards (up to four of them) but the firmware of the GC-TITAN RIDGE may need modification.
Some PCIe slot covers would need to be replaced (or drill some holes?) to connect 8 Thunderbolt ports and 12 mini DisplayPorts.
If you don't want to add additional Thunderbolt ports, then at a minimum, the MPX adapter would have:
4 x mini DisplayPort 1.4 inputs.
And you would only need one of those for max support.
So I'm not up to speed with Blender ... I've downloaded it and ProRender, and the Benchmark App ... how do I make it all blend to test my setup? And I'll be getting a 2018 MacMini i3 this weekend as an iTunes server to replace my 2014 MacMini i7 so I'll probably end up comparing the MBP to it as well ...