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

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

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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itsage
(@itsage)
Founder Admin
Joined: 4 years ago
 

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: 3 years ago
 

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

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Flint Ironstag
(@flint-ironstag)
Estimable Member
Joined: 4 years ago
 

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.

 

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zacanowski
(@zacanowski)
Active Member
Joined: 3 years ago
 

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?

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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manji_fa
(@manji_fa)
New Member
Joined: 2 years ago
 

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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Rafael Cichy
(@rafael_cichy)
Active Member
Joined: 3 years ago
 

Hi together,
i was able to run 3 eGPUs with an iMacPro at the office. At home connecting the 3rd eGPU to my nMP was not so successful.  Every time i plug in the 3rd, all eGPUs instantly running the fans at full speed and the display went black. regardless with buses are used... i have tried so many variations, but still no luck.

did anyone has any suggestions for my scenario?

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rhenriques11
(@rhenriques11)
Eminent Member
Joined: 3 years ago
 

Sometimes is a question of how you plug them. I was also facing the same problem in a MacPro 2013. Usually works if you plug at least two of them at exactly the same time. I also have more success when I plug them after a system login and then a logout. While in the users list, the plug in seems to be more successful.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Rafael Cichy
(@rafael_cichy)
Active Member
Joined: 3 years ago
 

thx for the fast reply....

... i will give it a try right now.

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MacBook Pro M1 | 16GB | 2 TB |
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OS X 11.4


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OliverB
(@oliverb)
Noble Member
Joined: 3 years ago
 
Posted by: rhenriques11

Sometimes is a question of how you plug them. I was also facing the same problem in a MacPro 2013. Usually works if you plug at least two of them at exactly the same time. I also have more success when I plug them after a system login and then a logout. While in the users list, the plug in seems to be more successful.

I cannot confirm this. I have been using 3 eGPU in MacOSX, too and there have been no issues at all. The necessity of a "logout" can come already with one single eGPU, but only for external display.

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