System specs :
2020 iMac 27" - i9-10910/RP 5500xt/40GB RAM/512GB SSD
2x 4K UHD Displays
eGPU hardware :
RTX 3090 + Razer Core X + included 0.5m Thunderbolt 3 Cable
Installation steps :
Installation was pretty straightforward compared to an AMD GPU:
1. Install Bootcamp and all included drivers
2. Hot-Plug eGPU and install newest drivers
To get both the eGPU and dGPU up and running there is an optional third step:
(3.) Hot-Plug the eGPU after Windows has booted
Though this results in some issues with Bluetooth.
Furthermore Cold-Plug only seems to work with this extra step:
(3.) Set BootCamp as Startup-Disk in macOS
Benchmarks :
I currently tested only 2 Games:
| Internal Display UHD | External Display UHD | |
| Horizon: Zero Dawn | ~30 - 35 FPS on highest Settings, massive Framedrops | ~45 - 60 FPS on highest Settings |
| The Witcher 3: Wild Hunt | ~45 - 50 FPS on highest Settings, massive Framedrops | ~60 - 75 FPS on highest Settings |
Both games seem to be heavily starved by bandwidth. Especially HZD where it made almost no difference in performance when I switched from 4K to 1440p.
Comments :
Here I want to share same lessons I learned while trying this build:
- Though the eGPU and dGPU can run at the same time, sometimes when trying to watch a YouTube video on the internal display either causes it to reload and use the dGPU or simply crash the whole System
- I had to take off the shroud of the Razer Core which resulted in a temperature drop of ~12 degrees and a reduction in fan noise. The heat this card generates is insane, even when undervolted.
- Gaming on the internal display seems to be hopeless. Though the frame rate at lower resolutions (1440p) is higher, you get annoying frame drops every few seconds.
- Trying to Cold-Plug without setting BootCamp as the Startup-Disk just results in a Blackscreen when booting.
- Sometimes Bluetooth just doesn't work. Probably an issue with resource allocation.
If you have any questions or Benchmark requests, let me know!
@sudelnuppe, you should be able to up the FPS in The Withcer 3 drastically by reducing "Foliage Visibility Distance" in the Graphics Options (has huge impact on the bandwidth).
Best regards
phila
did your 3090 came with a 3x8 pins?
Razer 15 advanced model (2019) 32gb/1tbssd 2070 maxq w/ Razer core x chroma (3080 evga ftw3 ultra)
@elel_penaflorida_mariano, No, it has a 2x8 configuration. It's a Palit RTX 3090 Gaming Pro PC
Nice build. Good to hear Windows 20H2 runs in Bootcamp without error 12 on your 2020 iMac. 😎
This is a pretty serious build! Have you ever test two eGPUs on your iMac? Or can it only handle a single eGPU?
Ryzen 9 3950x 16-core CPU
64GB RAM @ 2666 Mhz
1 TB SSD
RTX 2070 Super and GTX 1080 dGPUs
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
.