Connecting monitors to both eGPU and internal GPU OK? To avoid startup issues…
 
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Connecting monitors to both eGPU and internal GPU OK? To avoid startup issues…  

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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 

Hi all, first time poster here. Please be gentle.

tl;dr — is it OK to have a monitor connected to the internal GPU as well as monitors connected to the eGPU, or will that affect performance, and if so will it affect all systems or only things running on the GPU-connected display?

Full details and reason for the question…

I'm running a 2018 Mac mini 3.2 GHz 6-Core Intel Core i7 with internal GPU Intel UHD Graphics 630 and an eGPU Radeon RX Vega 56 8 GB in a Razer Core X Chroma Thunderbolt enclosure. 

The Vega card has four ports on it; three DisplayPort and one HDMI. I use three or even all four of them (when four are connected I'm having an issue that I'll do another post on later). 

For normal use, all is good.

However whenever I reboot, probably two out of three times I get nothing on screen. Totally black. The Mac appears to have booted up (power light is on, connected RAID is spinning), but I see nothing on screen and can't even remote log in to it (using Screens).

When that happens, I…

  1. Force shut it down
  2. Disconnect the eGPU
  3. Connect a display to the built-in HDMI port
  4. Boot up normally
  5. Connect the eGPU, which comes up fine
  6. Disconnect the HDMI monitor

Needless to say this is a pain in the ass. Then it occured to me… maybe instead of going through that each time, I'd just have one of my three monitors connected to the Mac mini's HDMI full time, and the other two on Vegas in the eGPU. But my instinct is that this is a bad idea.

So that's the question — is it OK to have a monitor connected to the internal GPU as well as monitors connected to the eGPU, or will that affect performance, and if so will it affect all systems or only things running on the GPU-connected display?

Also bonus round; why the heck does this happen each time I boot up in the first place?!

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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itsage
(@itsage)
Illustrious Member Admin
Joined: 3 years ago
 

@photojoseph,  Apple is still sorting out the firmware on the 2018 Mac mini regarding eGPU. It's one of the only Macs that can produce boot screen through a supported eGPU. This is rather buggy atm and my guess is it has something to do with the symptom you have been experiencing.

As long as the Mac mini iGPU connected monitor is not primary, there's not much to worry about regarding performance. It's the same scenario as a 13-in MacBook Pro that has the built-in display wired to the iGPU all the time.

 

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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 

@itsage,  OK thanks, that's good to know (and I didn't know about the known Apple issues). I'll move this third monitor to the iGPU and see how it goes! 

Back in the old days (talking 20+ years ago), my understanding was that VRAM was split between monitors, so if you had 2GB of VRAM and two displays, each only got 1GB. I now don't know if that was ever accurate, but from what I've been reading since getting this eGPU setup, that doesn't seem to be the case (anymore). I don't think it really matters how many screens you have connected… is that an accurate statement? 

 

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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julioleon
(@julioleon)
Active Member
Joined: 2 months ago
 

@photojoseph,  you can also try using “get info” on a per app basis. Inside the application info there is a button that tells the app to prefer the external gpu.

 

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 
  • @julioleon,  right! As I understood it, if your monitor(s) are on the eGPU, then that setting was irrelevant. But I guess if I’m using both GPUs then that becomes more important! Thanks. 

 

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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(@massimo_franzese)
Trusted Member
Joined: 4 months ago
 
Posted by: @photojoseph
  • @julioleon,  right! As I understood it, if your monitor(s) are on the eGPU, then that setting was irrelevant. But I guess if I’m using both GPUs then that becomes more important! Thanks. 

 

I have your same set up single eGPU connected to displays. Your concept still hold the VRAM is shared between display and so is the bandwidth of the bus therefore the video card in the eGPU determines how many screens you can drive and for what.

On static image you can connect 4 displays to the radeon and others to the mini static scenes are fine but if you were doing video playback at 4k for example there is a risk of saturating the card bandwidth

Though am not sure why you would playback video on more than 2 screens the limitation is given by the frames you can push through

In terms of the boot issue instead of reboot shutdown and boot in 99% of cases this works fine with eGPU

By the way your youtube channel has some useful stuff and I liked your DXO clips  

 

Mac Mini 2018 3.2 Ghz 6 cores
Razer Core X enclosure with Sapphire Vega 64 Nitro
Benq PD2720U


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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 
Posted by: @massimo_franzese

I have your same set up single eGPU connected to displays. Your concept still hold the VRAM is shared between display and so is the bandwidth of the bus therefore the video card in the eGPU determines how many screens you can drive and for what.

On static image you can connect 4 displays to the radeon and others to the mini static scenes are fine but if you were doing video playback at 4k for example there is a risk of saturating the card bandwidth

Though am not sure why you would playback video on more than 2 screens the limitation is given by the frames you can push through

OK, so the vram is basically dynamically allocated? As long as I'm only playing video on one screen (which of course I would be in an editing environment), then it shouldn't matter… and presumably as long as I'm not using the iGPU-connected display for playback, I should be fine.

In terms of the boot issue instead of reboot shutdown and boot in 99% of cases this works fine with eGPU

Oh interesting… OK, I'll try that. I think I'm more likely to hit restart than shut down so perhaps that's the key.

Given the oddity with the screen layout I saw in Final Cut with both iGPU and eGPU connected displays (Final Cut insisting on putting the browser on the iGPU display every time), I'd rather stay all external if I can.

By the way your youtube channel has some useful stuff and I liked your DXO clips  

Oh thank you!

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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(@massimo_franzese)
Trusted Member
Joined: 4 months ago
 

@photojoseph, final cut can manage the displays in the secondary display options 

you can then choose what does the primary and secondary do. It doesn’t manage more than two. I recommend you connect both displays to the eGPU and then you have the option of having one of media browser, timeline or playback on the secondary 

for grading purposes I find useful to have media browser and timeline on display 1 and playback on 2

avoid using the iGPU connected display for final cut as it will slow down everything 

 

Mac Mini 2018 3.2 Ghz 6 cores
Razer Core X enclosure with Sapphire Vega 64 Nitro
Benq PD2720U


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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 

@massimo_franzese, Right, that's how I have it. What I'm saying is that with the iGPU connected, whenever I open FCPX, it puts the browser on the iGPU-connected display. I can move it, and even save that as a custom layout, but it still will put it back on the other display after re-launch. Super weird. As far as I can tell, macOS is considering my eGPU-connected primary display #1 (as it should), but then calling the iGPU-connected display #2 and then the other eGPU-connected display #3, and FCPX wants to put its displays on #1 and #2. 

I think I need to find a way to force macOS to see the iGPU-connected display as the last in the chain. It probably is considering it first, but that's overridden by my defining another display as #1 (by putting the menu bar on it in System Preferences), so then the iGPU one becomes #2.

 

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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(@massimo_franzese)
Trusted Member
Joined: 4 months ago
 

@photojoseph, this is the primary reason to connect NO display to the mini. Just connected them all to the Vega 56

Are you short of ports? What connections are your monitors? May be worth investing in adapters 

Avoid the direct connection at all costs

 

Another tip disable system and security updates as they are not supported with eGPU connected. They need to be done with a screen connected to the main unit as reboots may turn sour...

 

Mac Mini 2018 3.2 Ghz 6 cores
Razer Core X enclosure with Sapphire Vega 64 Nitro
Benq PD2720U


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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 
Posted by: @massimo_franzese

@photojoseph, this is the primary reason to connect NO display to the mini. Just connected them all to the Vega 56

Are you short of ports? What connections are your monitors? May be worth investing in adapters 

Avoid the direct connection at all costs

No, that is what I want to do, but you've missed the start of this thread. Only eGPU-connected displays is what I've always done. But I'd found that on reboot, the vast majority of the time I'd get blank displays, and have to play an annoying game of force shutting down, disconnecting eGPU, moving a display to iGPU, rebooting, reconnecting eGPU, which then sometimes gave a super weird split screen display, and back and forth until I finally was back on eGPU entirely and could actually see things. This thread started because I was trying to avoid that issue. @itsage had said:

Posted by: @itsage

@photojoseph,  Apple is still sorting out the firmware on the 2018 Mac mini regarding eGPU. It's one of the only Macs that can produce boot screen through a supported eGPU. This is rather buggy atm and my guess is it has something to do with the symptom you have been experiencing.

As long as the Mac mini iGPU connected monitor is not primary, there's not much to worry about regarding performance. It's the same scenario as a 13-in MacBook Pro that has the built-in display wired to the iGPU all the time.

That made sense explaining why I was having this issue. So I tried using both iGPU and eGPU, and discovered the FCPX issue which is probably even more annoying, since I launch Final Cut way more often than I reboot my Mac.

Then you suggested shutting down instead of rebooting, and that's where I'm at now (all eGPU at the moment)

Another tip disable system and security updates as they are not supported with eGPU connected. They need to be done with a screen connected to the main unit as reboots may turn sour... 

oh good to know. I had auto OS updates off, but not security. Noted and fixed, thanks. 

 

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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(@massimo_franzese)
Trusted Member
Joined: 4 months ago
 

@photojoseph

Yes connect all to eGPU and do not reboot. Connecting a single screen to the Mini destroys Final Cut Pro acceleration and must be avoided

Only circumstance is temporary when updates are installed

 

Mac Mini 2018 3.2 Ghz 6 cores
Razer Core X enclosure with Sapphire Vega 64 Nitro
Benq PD2720U


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PhotoJoseph
(@photojoseph)
Active Member
Joined: 2 months ago
 

Thanks @massimo_franzese

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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