eGPU + 4K Monitor + MBP Screen

[rickeames]

I have a 13" MBP (2018), an LG 4K monitor, and the Blackmagic eGPU. When I run in clamshell mode, all is well and the GPU is fully active. What I want is to have it also be fully active if I open the screen to get both screens active. However, when I *do* open the screen, it switches to the built in graphics chip, which is suboptimal.

Is there some trick to making this work?

 

[lankox]

I have the same laptop, eGPU , and LG 5K. The eGPU appears to be active when my laptop is open. What makes you think the eGPU shutdowns when not in clamshell mode?

 

[rickeames]

Because with the lid open "About this Mac" shows the intel chip active. When I close the lid, it shows the eGPU active.

 

[lankox]

Hmmm. Here is a picture of my "About this Mac" with the lid open. Unless I'm missing something it does seem you have a problem.

 

[rickeames]

Weird. I just did this. Running clamshell and I'm on the Radeon. I then open the lid, and I drop to the Iris.

 

[lankox]

I just ran a series of tests of closing and opening the lid several times. About Mac always reported being on the eGPU. I did buy a 3rd party Thunderbolt 3 cable as I heard the ones that come from LG are cheap. Not sure if that makes a difference.

 

[rickeames]

I just ran a series of tests of closing and opening the lid several times. About Mac always reported being on the eGPU. I did buy a 3rd party Thunderbolt 3 cable as I heard the ones that come from LG are cheap. Not sure if that makes a difference.

Maybe it’s the way I’m running it? I have the laptop going into the blackmagic, then the blackmagic going to the monitor. Is that how you connect it?

 

[lankox]

Maybe it’s the way I’m running it? I have the laptop going into the blackmagic, then the blackmagic going to the monitor. Is that how you connect it?

Yes, both the laptop and monitor are connected directly to the Blackmagic.

 

[rickeames]

Alright -- last potential question: have you checked the "use eGPU" box for the app you're running currently? I have not enabled any app as I'm looking to get it "globally" without having to individually turn on particular apps. Outside of that, I can never get the eGPU to engage with the lid open and an external monitor connected, using the Blackmagic. Only closed.

 

[lankox]

Alright -- last potential question: have you checked the "use eGPU" box for the app you're running currently? I have not enabled any app as I'm looking to get it "globally" without having to individually turn on particular apps. Outside of that, I can never get the eGPU to engage with the lid open and an external monitor connected, using the Blackmagic. Only closed.

I have selected the use eGPU box for a handful of my apps but it is my understanding this is not necessary when connected to an external monitor.

 

[rickeames]

Hmmm, okay well I did some experimenting and found that with the lid open, even though my "About This Mac" says Intel, it's only using that for the internal display. So if I look at displays, it shows the internal running on intel iris, and the external using the eGUP. The GPU activity monitor bears this out showing activity with both chips. So, that at least clears that up. I know there is a script out there that can force the eGPU to drive the internal too, and I may go that route. Thank you for the assist!