Adding AMD GPU to iMac 2019

[bluesky_london]

Good morning everyone,

I have a 2019 iMac that I want to keep because of its excellent screen, as you all know. I work on very large photographs on Photoshop (1 gb+):
. 3GHz 6-Core Intel Core i5
. Radeon Pro 570X 4 GB
. 64GB 2667MHz DDR4
. 4Tb SSD
. 2Tb scratch disk

To further improve it's ability to deal with v large pictures, I am thinking of buying an external card SAPPHIRE Pulse AMD Radeon RX 6800 16 GB GDDR6 memory (the Radeon Series 7 seems not to be compatible).

I am not clear at all on which casing shall I use.
Can I ask you:
1) what do you think of this solution/configuration
2) can you suggest me a case in stock in Europe (I am based in France).

Thank you very much to you
Dan

 

[PaulD-UK]

Apple's list of enclosures is brief:

• Sonnet eGFX Breakaway Box 650W
• Razer Core X

So the latter might be appropriate?

Of course you will not be able to use the excellent iMac screen, if you connect to the external ports on the GPU...

 

[bluesky_london]

Thank you! but I am confused by this
> Of course you will not be able to use the excellent iMac screen, if you connect to the external ports on the GPU...

mmm, so I did totally miss the point - I was hoping to outsource the calculations to the Radeon RX 6800 but ofc continue using the Mac display. Am I dreaming?

 

[PaulD-UK]

No. I think it will work with the iMac screen displaying the output of the eGPU, but the re-encoding of the graphics back to the iMac over TB3 causes losses (of 25-30%?) to the acceleration on the internal screen image.
That is why Apple only describes using the direct eGPU output...
No good for gaming, maybe OK for photo image editing?

I use my old iMac 5K screen for an (excellent 5K) external monitor with DP input, but that is a different thread - nothing to do with this one... 😀

 

[bluesky_london]

Ah, so do I get you right? there would be a lag to display back the image onto the screen which would be an issue if gaming but most certainly not at all for image editing. Am I correct?

And no issue at all keeping using the iMac screen?

 

[bluesky_london]

So - thank you for the advices @PaulD-UK
I did get the enclosure and the card, and set it up.
It is recognized by the iMac at start-up time, but Photoshop doesnt seem to want to use it.
I guess it's now a question to an Adobe forum!

I will lyk if i make it work ...

best
Dan

 

[PaulD-UK]

There must be different instructions for getting Photoshop to work with the eGPU on the iMac screen.
There are some instructions, here’s two that show up in a search:

Or:

How To: eGPU-Accelerated Internal Display in macOS | eGPU.io

egpu.io

 

[bluesky_london]

Well, sadly not and followed all instruction from Claude and ChatGPT.
Here is the post on Adobe's forum

eGPU for iMac2019

Hi, I work on v large psb files - think 25k pixels by 30k, w/ layers and masks. I have a 2019 iMac that I want to keep because of its excellent 5k screen. Here is my setup 3GHz 6-Core Intel Core i5 Radeon Pro 570X 4 GB 64GB 2667MHz DDR4 4Tb SSD 2Tb scratch disk To further improve the...

community.adobe.com

 

[bluesky_london]

thank you @PaulD-UK . I had not realised our emails crossed, so I do now explore your additional solutions.
The set-eGPU script is not lucky so far - allegedly terminal doesnt has right on the whole system, despite I gave them.
I will have more time this weekend to experiment. Thanks for bearing with me!

Dan

(edited for spelling)