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The eGPU Apple should have built years ago  


New Member
Joined: 9 months ago

Hi everyone,
here's my first (and possibly last) eGPU custom build. I got the inspiration for this from this thread:
Specifically from this thread:
So thanks and credits to user hoeveler for the inspiration!

In theory it will be able to scale up to 8 GPU's, at the time of writing I only own 3 relatively powerfull GPU's but I only just started collecting Smile

It's a used PCIe expansion backplane from Cyclone Microsystems the PCIe2-429 (Plus the PCIe2-436 Upstream Adapter Card and the PCIe2-426 Host Adapter Card).

I've decided instead of buying a cheap and ugly housing somewhere, that I could repurpose an old Powermac G5 housing and adapt it for this project. Recycle to save the planet I guess...
People might love or hate Apple for various reasons, but let's all agree: they build nice looking housings!

I work with both PC's and Mac's. I like them both.
As far as I know, with OSX I currently don't have good Nvidia CUDA Support and most GPU Render engines need it, at the moment my main machine is a HP z820 Workstation with 2 x E5-2690 Xeons and 128GB of RAM...old, affordable but still lots of PCIe lanes.

Of course this project took much longer than I expected. Initially I thought that the housing would be really spacious for just a small 1700W  Power supply and up to 8 GPU's and some fans....turns out I was wrong. 
It took quite some time on the CAD to find a solution where I would not block any of the PCIe Slots and still have some relatively OK concept for the cooling airflow.
I think the current solution is quite ok, but I might need to add many more fans on the bottom of the housing, and maybe also some exhaust fans at the top....I will simply monitor my temps with each GPU I will add in the future, and improove my current solutions if it starts to become necessary.

I ended up with 3 custom sheet metal parts that could be laser cut in a nearby shop. After some improvised bending, some thread cutting, sanding and some painting it looks ok. I tried to not disturb the classic look of the mac too much, so no RGB or other fancy things. After some dremel modifications on the housing and some hunting for the correct sized distance bolts and such all could be assembled and tested.

I use my eGPU's just for 3D rendering with Redshift renderer, not for gaming. 
This setup would be less than ideal for gaming, as there is zero support for SLI/Crossfire. So having the ability to put up to 8 GPU's in a system would really make not much sense for gaming.
Also, as the backplane is just PCIe2 speed not all GPU's would perform ideal in realtime gaming applications. 

But, for non-realtime rendering with Redshift it works like a charm so far...although I have to admit I could only test it with 3 GPU's so far. In my tests I saw no difference between having the GPU internal in my host PC or external in my eGPU. For non realtime rendering applications, PCIe bandwidth seems to be less criticial after a certain level. I've read people not having much luck with rendering when they just tried to use USB to PCIe Riser cards which are normally used for mining. Also Redshift Support does not recomend or support these in any way. Therefore I hunted down a PCIe Expansion Backplane to build my dream render machine.

There are turnkey solutions for an expansion like this, but they can get really expensive. 
Honestly, my solutions was also not cheap in the end and if I would calculate how much time I needed to design and build this, I should have probably just bought a turnkey solution. Anyways, it was fun to do this project and I hope some of you will like it!

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


Flint Ironstag
Estimable Member
Joined: 3 years ago


MP 6,1 | 4c | d700
MP 6,1 | 6c | d500