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2 Nvidia eGPUs working on an iMac Pro, 3rd doesn't work?  

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zacanowski
(@zacanowski)
Active Member
Joined: 1 year ago
Posts: 6
April 6, 2018 5:31 pm  

hi all,
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)
Many thanks!
Zac

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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theitsage
(@itsage)
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Joined: 2 years ago
Posts: 3813
April 6, 2018 6:37 pm  

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.

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zacanowski
(@zacanowski)
Active Member
Joined: 1 year ago
Posts: 6
April 6, 2018 6:43 pm  

Thank you very much for your reply theitsage, that makes sense.

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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Flint Ironstag
(@flint-ironstag)
Estimable Member
Joined: 2 years ago
Posts: 166
April 6, 2018 8:38 pm  

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


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zacanowski
(@zacanowski)
Active Member
Joined: 1 year ago
Posts: 6
April 6, 2018 9:30 pm  

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?

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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manji_fa
(@manji_fa)
New Member
Joined: 4 months ago
Posts: 4
March 24, 2019 12:06 am  

I’m trying to pm you to ask some suggestions about my iMac Pro.
it seems pm doesn’t work :/

iMac Pro 14 | 64GB | Vega 64


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