2020 27" iMac (RP5500XT) [10th,10C] + RTX 3090 @ 32Gbps-TB3 (Razer Core X) + Win...
 
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2020 27" iMac (RP5500XT) [10th,10C] + RTX 3090 @ 32Gbps-TB3 (Razer Core X) + Win10 20H2  

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Sudelnuppe
(@sudelnuppe)
New Member
Joined: 4 years ago
 

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:

  1. 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
  2. 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.
  3. 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.
  4. Trying to Cold-Plug without setting BootCamp as the Startup-Disk just results in a Blackscreen when booting.
  5. Sometimes Bluetooth just doesn't work. Probably an issue with resource allocation.

If you have any questions or Benchmark requests, let me know!

2020 27" iMac (RP5500XT) [10th,10C] + RTX 3090 @ 32Gbps-TB3 (Razer Core X) + Win10 20H2 [build link]  

Mini i5 and itsage liked
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phila-delphia
(@phila-delphia)
Eminent Member
Joined: 11 months ago
 

@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

 

2019 15" Lenovo Yoga C940 (GTX1650) [9th,6C,H] + RTX 2070 Super @ 32Gbps-TB3 (Razer Core X Chroma) + Win10 [build link]  

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ElEl Penaflorida Mariano
(@elel_penaflorida_mariano)
Active Member
Joined: 1 month ago
 

did your 3090 came with a 3x8 pins? 

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

.

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Sudelnuppe
(@sudelnuppe)
New Member
Joined: 4 years ago
 

@elel_penaflorida_mariano, No, it has a 2x8 configuration. It's a Palit RTX 3090 Gaming Pro PC

 

2020 27" iMac (RP5500XT) [10th,10C] + RTX 3090 @ 32Gbps-TB3 (Razer Core X) + Win10 20H2 [build link]  

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Mini i5
(@mini-i5)
Honorable Member
Joined: 1 year ago
 

@sudelnuppe

Nice build. Good to hear Windows 20H2 runs in Bootcamp without error 12 on your 2020 iMac. 😎

 

2018 Mac Mini i5 / 6-core 3.0-4.1 Ghz / 32GB / 256GB / Intel UHD 630 / PowerColor Gaming Station / PowerColor dual-fan RX 5700 XT / Mac OS 10.15.6 Catalina / Windows 2004 😏 / Dual LG 27" 4K displays


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