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 performance with v large pictures, I bought
- an external GPU, a SAPPHIRE Pulse AMD Radeon RX 6800 16 GB GDDR6 memory (the Radeon Series 7 seems not to be compatible)
- enclosed in a Razer casing
The card is recognized by the Mac, all good here. However I have the feeling it's not used at all by Photoshop.
- In Photoshop/Settings/Performance it continues displaying the internal AMD Radeon 570 card w/ 4 Gb, not the eGPU 5700 with 16.
- When looking at Activity Monitor and using Camera Raw, Perspective Tilt, Liquify, I dont see any usage of the 5700.
To be absolutely honest, I brefly saw some activity on the eGPU, see snapshot, but the bulk of the activity seems to always be anyway on the built-in card.

Thoughts? Was I naive thinking Photopshop would be using the eGPU?
I use Photoshop 2025 and Sonoma 14.5.
Thank you all
Dan
