Mac Mini 2018 LG 5k Monitor eGPU Connection

[gimbalboy]

Hi there, does anyone know if it's possible to power a LG 5k monitor from one of the TB3 ports on a Mac Mini while a non-BlackMagic eGPU is connected to another Mac Mini TB3 port?

I know this is not the most efficient connection (which would be Mac -> eGPU -> Monitor), but I want an upgradable eGPU that will better accelerate full-screen video playback or encoding. Will the OS UI benefit from eGPU acceleration when connected in this manner?

 

[Krevnik]

It will work. The 5K just needs the DisplayPort bandwidth and USB connection. It doesn’t need any of the TB3 bandwidth.

It won’t get any acceleration from the eGPU by default though. While there’s been some luck routing frames back across the TB3 cable for accelerating a laptop display, I haven’t seen anyone do it for a 5K. It may work though. You do pay a performance penalty doing it that way though.

I’m a bit surprised someone hasn’t made a puck with dual DisplayPort inputs Along with USB, and a TB3 output so you can drive a TB3 monitor like the 5K with a regular GPU.

 

[yukari]

Won't it just use its internal GPU through TB3 port to power the monitor?
I just don't see a signal going through TB3 to eGPU and back to Mac Mini to the monitor.

 

[Krevnik]

Won't it just use its internal GPU through TB3 port to power the monitor?
I just don't see a signal going through TB3 to eGPU and back to Mac Mini to the monitor.

Correct:

It won’t get any acceleration from the eGPU by default though.

However, you can still use it for Metal and similar acceleration of things that can use it as general compute and it still works.

Case in point: I can drive my display via a USB-C -> DisplayPort connected to the Mini, and Affinity Photo will still be able to work a bit faster with an eGPU connected, vs not. But it can use Metal to accelerate compositing and effects. So it is more like: App has Work -> eGPU crunches data -> App gets result and writes it to iGPU for display.

I should probably mention that in this setup, the app has to support Metal compute for it to work.

I use it this way myself right now, but more because my eGPU + DisplayPort switch seems to have issues.