How To: eGPU-Accelerated Internal Display in macOS  

It should work with your iMac late 2013. The performance difference is not that significant if you use the eGPU with an external display. Internal display eGPU usage will be a big hit on performance through Thunderbolt 1 connection.

How about the internal egpu acceleration for Windows? Does that work and will it require the workaround? Thanks.

Is it possible to use eGPU for MacBook Pro Retina Late 2014? With Nvidia 1070 ....can I also use internal MacBook display if I bootcamp? Also what about VR support?

This method doesn't work well with in full screen case. You can simply follow step 2 to 6. Then mirroring the display. After that, you will have a eGPU-Accelerated full screen application working fine with your internal display.

Sometimes, the application will launch from second display, I don't know why. You can solve it by switching the primary display then launch and mirroring. It looks like impossible to launch Steam client on second display.

Download and run DisableMonitor
Go to macOS System Preferences -> Dock -> Position on screen -> Left (if you arrange your ghost display to the right of the internal display)
Plug the ghost display adapter in and set it as the primary display
Set the resolution to match internal screen in DisableMonitor*
Launch an app such as Valley benchmark from the Dock (there you see its child window)

Will this work on a PC?

You don't need this workaround on Windows. Both Nvidia and AMD has software solution to make eGPU accelerate the internal display.

Would you point us in the right direction?

Will this work if i want to use my imac as a screen for a signal comming from a pc with displayport 1.3?

I'm not sure. That seems like it's not related to eGPU. Can you elaborate on your plans?

Question. Is it possibe to manage it with installing windows 10 by using internal fake display accelerated eGPU?