MacBook - Duel Screen Issue (disable TB3?) (eGPU)
 
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MacBook - Duel Screen Issue (disable TB3?) (eGPU)  

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solomani
(@solomani)
Eminent Member
Joined: 7 months ago
 

I believe I know what is happening but wondered if this was an issue or if there was a workaround.  My setup:

  • MacBook 2019 in dock.
  • Dock is connected via tb3 to my monitor.
  • Dock is also connected to an eGPU
  • eGPU is connected to the monitor via HDMI.
  • Under macOS Catalina 10.15.5 (I believe this wasn't an issue under 10.15.4).

What seems to be happening is the MacBook is outputting to both the TB3 and HDMI at the same time. Using the onboard Vega20 via TB3 and using the HDMI. No idea if this impacts performance - doesn't seem to - but I want to disable the TB3 video output. At the moment, I have to mirror to have the setup work correctly:

https://discussions.apple.com/content/attachment/5f59ab82-c522-4f75-8e5f-94742930b860

https://discussions.apple.com/content/attachment/049c9a88-aac8-4919-813c-f4aed4815c7d

My other solution is to plug the dock in to the non-monitor thunberbolt3 which is only 15w - as opposed to the 85w tb3/monitor plug. But I assume if I switch these the MacBook will charge slower?

Thanks in advance.

2019 15" MacBook Pro (Vega20) [9th,8C,H] + RX 5600 XT @ 32Gbps-TB3 (Razer Core X Chroma) + macOS 10.15.4 & Win10 17763 [build link]  

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itsage
(@itsage)
Illustrious Member Admin
Joined: 4 years ago
 

@solomani, Don't put the eGPU behind a TB3 daisy chain. The 2019 15-in MacBook Pro has two sets of TB3 controllers so make the most of them by connecting the dock on one side and eGPU on the other. Power Delivery will be from the Razer Core X with 100W rating.

Also the Samsung C34j79x has multiple monitor inputs including DisplayPort. I'd recommend using DP off the eGPU instead so that the dGPU does have to handle any external monitor. 

 

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2020 15" HP Spectre X360 [11th,4C,G] + RTX 2080 Ti @ 32Gbps-TB4 (AORUS Gaming Box) + Win10 2004 [build link]  


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solomani
(@solomani)
Eminent Member
Joined: 7 months ago
 

Hi @itsage, I use the monitor as a hub so that's why there is a connection from the dock to the monitor so my keyboard, etc works.  Plugging the MacBook into the Samsung 15w TB3 solved the double monitor issue.  I am assuming the dGPU is now off/not working in this setup - at least it seems to be when I check preferences.  Or are you suggesting I should not connect the MacBook at all via tB to the monitor to make sure the dGPU is not working?  Use the dock as the hub instead?

Having said that I will shift the egpu to the other side - I guess this improves performance which is good.  But why DP instead of HDMI? I thought it was much for muchness?

2019 15" MacBook Pro (Vega20) [9th,8C,H] + RX 5600 XT @ 32Gbps-TB3 (Razer Core X Chroma) + macOS 10.15.4 & Win10 17763 [build link]  

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