4k iMac, Skylake, TB3?

[mjohansen]

The answer is yes, sort of. I've been using an eGPU+GTX970 for a few months now on my iMac and MBA. Both of these machines only have Thunderbolt 1 ports, but gaming has been markedly improved on both machines (Windows and OS X). You cannot use solely the iMac's screen - you would need to use an external monitor from the eGPU. Nvidia Optimus is an option for macs that have only Intel GPUs, but I haven't bothered with this yet.

Check out more here: http://forum.techinferno.com/diy-e-gpu-projects/

Why can't you use the iMacs screen?

 

[martinm0]

Why can't you use the iMacs screen?

It's just not how it works. The iMac has a dedicated GPU driving the internal screen, so the eGPU would have to do all the processing and rendering, pass it back down the TB port to the iMac and the iMac's GPU would have to mirror what is sent. This is effectively how the Nvidia Optimus software works in Windows (but I believe that only works with Intel integrated GPUs). I do believe I was able to start up games on the eGPU in windowed mode and move them to the iMac's screen, but the performance was not great.

So the real win would be a cheap Mac Mini or MBA that drives the eGPU and an external display for gaming. (Or, obviously, being able to pipe the video back into the gorgeous iMac screen).

 

[mjohansen]

It's just not how it works. The iMac has a dedicated GPU driving the internal screen, so the eGPU would have to do all the processing and rendering, pass it back down the TB port to the iMac and the iMac's GPU would have to mirror what is sent. This is effectively how the Nvidia Optimus software works in Windows (but I believe that only works with Intel integrated GPUs). I do believe I was able to start up games on the eGPU in windowed mode and move them to the iMac's screen, but the performance was not great.

So the real win would be a cheap Mac Mini or MBA that drives the eGPU and an external display for gaming. (Or, obviously, being able to pipe the video back into the gorgeous iMac screen).

Hopefully somehow (in the future) it will be able to send the video back to the iMac screen.

 

[mjohansen]

It's just not how it works. The iMac has a dedicated GPU driving the internal screen, so the eGPU would have to do all the processing and rendering, pass it back down the TB port to the iMac and the iMac's GPU would have to mirror what is sent. This is effectively how the Nvidia Optimus software works in Windows (but I believe that only works with Intel integrated GPUs). I do believe I was able to start up games on the eGPU in windowed mode and move them to the iMac's screen, but the performance was not great.

So the real win would be a cheap Mac Mini or MBA that drives the eGPU and an external display for gaming. (Or, obviously, being able to pipe the video back into the gorgeous iMac screen).

As far as I understand, one of the new features of Metal is that it can benefit from several GPU's. Do you think this will be the answer to a plug'n'play solution where you can use the iMac screen?