I had wanted to get an iMac for an eGPU implementation in a while. The mid 2017 refreshed iMac with Thunderbolt 3 is perfect timing. I got the base 21.5" 4K which has the Radeon Pro 555 dGPU. It came from the factory with 10.2.4 so Goalque's automate-eGPU script should work fine under macOS. My priority is to get this iMac going in Windows 10.
One bad news is that Apple firmware completely disabled the iGPU in this iMac. I could not see it in either macOS or Windows (using goalque's guide). Therefore, the discrete graphics card Radeon Pro 555 is only one running all the time. That means AMD XConnect and Nvidia Optimus for internal display acceleration is not possible in Windows.
...unless you follow enjoy's excellent trick to force the eGPU accelerate the internal display with a headless display adapter. Here are the steps I took in order to get an Nvidia GTX 980 Ti going with this 2017 iMac 4k:
- Download Windows 10 ISO and install through Boot Camp Assistant.
- Allow Apple Boot Camp drivers to finish installation and shut down.
- Use a delay boot to hot plug the eGPU (OPTION key to select Windows volume, hot plug eGPU when Windows logo appears).
- Open Device Manager and right click on Microsoft Display Adapter and proceed to let Windows download the right drivers.
- Shut down and use delay boot to hot plug eGPU.
If all goes well the Nvidia eGPU should be fully functional with an external display after these 5 steps. I did not encounter error 12 with one eGPU. When I paired two eGPUs with this iMac, error 12 became an issue. For internal display eGPU acceleration, please read enjoy's guide. Here are my screen captures of the setup. Look at HWiNFO64, the Thunderbolt 3 PCIe lanes attach directly to the quad-core i5 CPU.
 |
 |
 |
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RTX 2080 Ti @ 32Gbps-TB3 (AORUS Gaming Box) + Win10 2004 [build link]
So, this is working on the internal display, with Win 10 at 4K?
2017 15" MacBook Pro 2.9GHz Core i7, Radeon Pro 560, OWC Mercury Helios FX 650, Sapphire RX590 8GB, ASUS MG24UQ
So, this is working on the internal display, with Win 10 at 4K?
Yes it does. As mentioned in my original post, it's a current workaround by following enjoy's guide to force the eGPU accelerate the internal display via a headless display adapter. Another limitation is "window mode" only for gaming.
I'm not sure why Apple disabled the iGPU on this mid-2017 iMac. If you have a mid-2017 iMac, please check System Information » Graphics/Displays and let us know whether iGPU is present.
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RTX 2080 Ti @ 32Gbps-TB3 (AORUS Gaming Box) + Win10 2004 [build link]
Mine is a 2015. I haven't tried it yet, TB2 being a huge reason.
2017 15" MacBook Pro 2.9GHz Core i7, Radeon Pro 560, OWC Mercury Helios FX 650, Sapphire RX590 8GB, ASUS MG24UQ
I agree. On older Thunderbolt connection, force-feeding the signal back to the internal display will absolutely negate eGPU performance gain.
In macOS, headless display workaround has a performance hit of 30-50%. I would imagine it's similar in Windows. I will try external display this week to get some idea on this mid-2017 iMac 4k.
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RTX 2080 Ti @ 32Gbps-TB3 (AORUS Gaming Box) + Win10 2004 [build link]
Cool! Thanks for ALL you and the guys are doing for the Mac Community.
2017 15" MacBook Pro 2.9GHz Core i7, Radeon Pro 560, OWC Mercury Helios FX 650, Sapphire RX590 8GB, ASUS MG24UQ
I agree. On older Thunderbolt connection, force-feeding the signal back to the internal display will absolutely negate eGPU performance gain.
In macOS, headless display workaround has a performance hit of 30-50%. I would imagine it's similar in Windows. I will try external display this week to get some idea on this mid-2017 iMac 4k.
@itsage It's a bummer that a headless adapter is needed for internal display support. I was hoping it would be possible without one, but my former 2014 5k retina only listed the dGPU as well. I don't think the 2017 iMac's are unique in this regard as this is an issue with other iMacs and the 2013 Mac Pro as well.
Do you foresee any possibilities to go around this (i.e. did you try disabling the dGPU once you got the eGPU setup working on boot? --or would that shut off internal display?
I'm interested to see the external display performance. I'm eying a 2017 5k retina, but I need to justify that egpu performance (e.g. 1080 ti, upcoming Vega) would outweigh the internal Radeon Pro 580 for future-proofing.
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
.I didn't disable the dGPU to see what would happen. I can try that later this week along with external display tests.
On the nMP, the Xeon CPU doesn't have iGPU. The Kabylake CPUs have iGPUs but Apple firmwares disable them unfortunately.
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RTX 2080 Ti @ 32Gbps-TB3 (AORUS Gaming Box) + Win10 2004 [build link]
I ran some quick benchmarks to compare Radeon Pro 555 dGPU vs GTX 980 Ti eGPU with external display. If you reference to the internal display eGPU results in my original post, it's about a 50-60% drop in performance. I really wish Apple had enabled the iGPU in this iMac firmware. Nvidia Optimus would have reduced that performance loss to 10-15%.
 |
 |
 |
 |
 |
 |
• external graphics card builds
• best laptops for external GPU
• eGPU enclosure buyer's guide
2020 13" MacBook Pro [10th,4C,G] + RTX 2080 Ti @ 32Gbps-TB3 (AORUS Gaming Box) + Win10 2004 [build link]
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
.