2 Nvidia eGPUs working on an iMac Pro, 3rd doesn't work?
I got 2 Sonnet 550 eGPU's with 1080 ti's working nicely with my Imac Pro, but I tried to add a third and all the boxes switch off when I log out, when all 3 are connected, and there's a black screen.
Does anyone have any ideas about how to get all 3 working, or why they don't? I'm on High Sierra 10.13.3 (17D2104)
Most recent builds of macOS allow one eGPU per Thunderbolt controller. The iMac Pro has two TB3 controllers and therefore can handle up to two eGPUs. I have not found any official documentations from Apple on this but this has been the case with my testings as well as others.
Thank you very much for your reply theitsage, that makes sense.
Couple of other things:
- arbitrary MacOS limit of 4 GPUs, period (used to be higher than this a few versions back)
- recent Macs won't boot with more than 2 eGPUs attached, no matter what fashion, different TB buses, etc.
I have tested OSS Cube3 & Cube2, each with 2 Nvidia cards installed (1080s or 1070s at the time). A 6,1 will boot with 2 cards in a single external enclosure, or with occasional futzing , 2 separate Cubes with 1 GPU each. Adding a 3rd eGPU to the mix = no joy.
MP 6,1 | 4c | d700
MP 6,1 | 6c | d500
Thanks for your info Flint - Bizon help also said there are not enough PCI-E lines for 3 eGPUs on Thunderbolt buses. It sounds like an amazing plan to have a box that holds more than one GPU. Do you think there may be any hope in the future? Just when I was getting addicted to GPU rendering it looks like I may have reached the limit until I get a different machine?