iMac (Retina 5K, 27-inch, Late 2015) + NVidia GeForce 1080ti possible?
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iMac (Retina 5K, 27-inch, Late 2015) + NVidia GeForce 1080ti possible?  


New Member
Joined: 2 years ago

Hi everyone this is my first post and probably the last before i jump out of a window with a iMac attached to my ankles or by a PC after 20 years of Mac Os.

It´s been a couple of months trying to read everything about OpenCl, Metal, CUDA, eGPUs and still not a conclusion and i can´t afford (literally) to go wrong.
First of all let me say, i don´t care about gaming at all, i need this for working purposes only. I will try to be straight to the point but it´s not easy apparently.

My built:

iMac (Retina 5K, 27-inch, Late 2015)
Processor 4 GHz Intel Core i7
Memory 16 GB 1867 MHz DDR3
GPU AMD Radeon R9 M395X 4096 MB
macOS Sierra 10.12.6

My problem:
I want to use CUDA for fast renders and Interactive Render Preview.
I only have 2x Thunderbolt 2 ports Up to 20 Gb/s (that´s what system report says)
I need an eGPU with NVidia to have CUDA
There are no drivers for the new 20 series of NVidia so the best option would be 1080ti GPU and a enclosure with enough power.

1. Is it possible to do it or the 5k retina display will not be supported?
2. Is it possible if you add an external monitor and keep the AMD internal driving the 5k display?
3. Is it possible to drive the 5k internal display if i get the Ghost Adapter? will it slowdown drastically the Interactive Render preview window? Does it matter on render times?
4. If i add an external monitor can i have just a crappy one for the Interactive Render Window and work on the internal 5k display driven by AMD?
5. How bad is the Thunderbolt 2 speed (is it enough to drive the 1080ti and take advantage of all CUDA cores and memory)?
6. If everything works, can i buy a second enclosure and GPU and have it connected to the second Thunderbolt port having 2x eGPU with 2x NVidia 1080ti and cut in half render times?

Thank you so much in advance.

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


Estimable Member
Joined: 4 years ago

My best guess says this... driving 5K external would be difficult with Nvidia eGPU ( I think blackmagic eGPU can do it but that's AMD ). Getting AMD and Nvidia working in tandem will be difficult too (one will likely have to be disabled). I think cuda cores would help render in davinci resolve , but not necessarily other apps. Probably better luck with motion design/ 3D renders than other video compositing renders (non-computational has disadvantage). Daisy chain eGPUs has been shown to be recognized if start of chain from computer has AMD then Nvidia (or is it the other way around?). Recognized but not accelerated (yet). I think 10.13.6 has better eGPU support than sierra (but obviously stay away from Mojave with Nvidia cards).

Before jumping out the window can you update your signature so others can follow your posts with more context? I'm looking to add an eGPU to my iMac 2013 with TB1. It is taking a while because of bootcamp install issues. Which brings me to my next suggestion... you should consider putting bootcamp on your iMac to work around some of the issues you may encounter with OSX. Lots of your above questions are only going to be narrowed down by putting a little money into a budget eGPU and start testing things out. There are new solutions found here every month but only through testing.

iMac 2013 10.14.1, Macbook Air 2013 10.11, MBP 2016 13" 10.13.6 , HP 4530s 10.11, node lite, DA-2 PSU w/mod, PE4L 2.1b expresscard34, GTX460,1050Ti,1060,1070/Ti RX470,560,580

2016 13" MacBook Pro [6th,2C,U] + GTX 1060 @ 32Gbps-TB3 (AKiTiO Node Lite) + macOS 10.13.6 [build link]