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I have a late 2016 15” MacBook Pro with a Radeon Pro 455 with 2GB VRAM.

I have upgrade to macOS High Sierra because its support external GPUs.

I have purchased Sonnet eGFX Breakaway Box with 550W Power Supply and installed NVIDIA GEFORCE GTX 1080.

I cannot get this setup to use the eGPU to power the internal screen.

How can I do this? Is this possible?

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Okay, first things first. Yes, this is possible, but at present it’s not officially supported yet. Apple did demonstrate an iMac Pro doing this back in December, so we know official support will come, it’s just not here yet.

If you want to do this now rather than wait, a member of the eGPU forums has successfully done this. Below are the steps involved, but please read them carefully as you should be aware it does come with potential risks!

  1. Purchase a ghost display adapter such as the NewerTech HDMI Headless Video Accelerator
  2. Download Spectacle and run it
  3. Download DisableMonitor and run it (IMPORTANT: Be sure to read the warning on their page!)
  4. Go to Apple > System Preferences > Dock
  5. Select the Left radio button for Position on Screen (assuming your ghost display adapter is set to the right of your screen - otherwise opt for the Right option instead)
  6. Now plug the ghost display adapter you bought at Step 1 into your eGPU and set it as your primary display
  7. Use DisableMonitor (from Step 3) to set your resolution to match that of your internal screen
  8. You can now use the relevant keyboard shortcuts to switch between your “displays”

NOTES:

  • You can run benchmarks like Unigine Valley and/or Unigine Heaven to test your setup works
  • Using a eGPU to feed the signal back to the internal display via the same Thunderbolt 3 connection does result in a performance hit of about 30% as compared to using the eGPU with an external display. However, your internal display will still work with better frame rates, etc compared to the built-in GPU.
  • Full instructions and other information can be found here.
  • I have no affiliation with any of the hardware/software referenced above.
  • Interesting! Who is right? You or Tetsujin? – eg pu Apr 18 '18 at 10:23
  • Well, we both are. Tesujin's answer and my second sentence: "Yes, this is possible, but at present it’s not officially supported yet." complement each other. In fact, I'm going to upvote his answer because it is officially correct at this point in time. What the guys at the eGPU forums did was basically circumvent point 4 of what Tetsujin quoted from the Sonnet eGPU Manual. If I were you, I would actually wait for Apple to support this usage. I say that because they themselves demonstrated this usage to the media in December, so support for it must be coming. – Monomeeth Apr 18 '18 at 10:24
  • This work for me. I use the fit-Headless GS - high resolution display emulator for game-streaming and VR in the page you link to, not the NewerTech HDMI Headless Video Accelerator. My screen better frame rates now so much smoother when play games! – eg pu Apr 26 '18 at 21:41
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I'm pretty sure they're not designed to accelerate your internal screen, only external, plugged into the eGPU itself.

From the Sonnet eGPU Manual

  1. Set up your monitor(s);
    To obtain the best graphics acceleration for applications like games, set a display connected to the eGPU as the main monitor. Open System Preferences:Displays, select Arrangement and drag the white menu bar to the external monitor. Drag the monitors to mimic the physical arrangement. If you want to tile your displays into one large space, Open System Preferences: Mission Control. Uncheck Displays have separate Spaces.
  2. Note that if you mirror an internal and external display together, internal graphics will be used.
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There is now an easy to use command line script called set-eGPU that solves this problem.

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My apps are being powered up by EGPU. I think what you need to do now is "go to get info by right clicking the application in Applications folder and then check prefer-External GPU" That's all

[![In the applications folder, get-info shows this:

or this link that may help you more clearly. https://support.apple.com/en-us/HT208544

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Sadly, many apps don't have support for an eGPU powering the internal screen only external sorry. Apple doesn't have official support for it on an internal screen and developers have to code it into their apps and will cause notable performance drops compared to using an internal display. Also, the GTX 1080 also doesn't have official support from Apple so even using it on an external display may be challenging. https://support.apple.com/en-us/HT208544

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