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CUDA support disappears when plugging in external GPU
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Hardware: Dell XPS 15, Win10, internal GPU GTX1050, external GPU GTX1080Ti (in Akitio Node via Thunderbolt 3)
Blender: 2.78c (also 2.80)
Latest versions of Thunderbolt drivers, akitio firmware, nvidia drivers

Just using the notebook without the external GPU: everything works fine.
Also the eGPU works correctly (nvidia control panel shows both GPUs, monitor on eGPU works, games and benchmarks work, ...)

But when the eGPU is connected to the PC, there are no more GPU options in the user preferecens "cycles compute device" (it only shows "None" ... not even the internal GTX1050 that always works when no 2nd GPU is connected)

I just bought the Akitio Node + GTX 1080 Ti in hopes to speed up rendering times and the setup works as one can only dream of EXCEPT for what I actually wanted to use it for: blender cycles :(



Event Timeline

Two things to check:

Also, did you install the drivers from What is the exact driver version?

Brecht Van Lommel (brecht) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Jul 25 2017, 6:02 PM
Chris (crazychris) added a comment.EditedJul 25 2017, 6:57 PM

Yes, drivers are from nvidia. Control panel shows version 384.94
BUT Cuda-Z says "no compatible CUDA devices found" when the external gpu is plugged in :-(
... but nvidia gpu monitor shows eg Chrome running on the GPU (???)
any ideas?

After playing around with this setup now for a day I just found this link
where the user disabled the internal nvidia GPU and then the external GPU worked in CUDA-Z (!)
... and now it works in blender too!
(not a perfect solution but at least I didnt buy the Akitio +1080Ti for nothing - and maybe nvidia can fix this in the future)
PS: THX brecht for your help!

Brecht Van Lommel (brecht) claimed this task.

Ok, good to hear you found a solution, sounds like there is not much we can do about this in Blender.