Using the LG 5k Display as an External Monitor (attachment to a eGPU)
 
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Using the LG 5k Display as an External Monitor (attachment to a eGPU)  

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JonRoth
(@jonroth)
Active Member
Joined: 3 years ago
 

I've been looking for a solution that will allow me to use my LG 5k display as an external monitor with my eGPU. However, due to it's thunderbolt 3 only connectivity, it wont connect to any GPUs at the moment. Furthermore, due to Apple being one of the only people to convert two display ports into 1 single thunderbolt 3 port, I have come to terms with the fact that as of right now, I won't get 5k resolution in bootcamp. But, I can get 4k.

To use the LG 5k currently, I need to plug it directly into my mac via thunderbolt 3, and because of that, the eGPU takes more performance hits as the signal needs to feed through the controller in the macbook and furthermore, the LG 5k is considered an internal GPU (according to research done on this forum) making the whole process of switching between operating systems cumbersome (activating iGPU only to use with internal display, deactivating the dGPU, etc).

But I may have found a potential solution that allows me to use the 5k display as an external display. It requires two adapters, and I'm curious as to the performance loss when using them. Anyway, here's my thought process:

1. Use the displayport out on the eGPU and connect it to a Displayport to minidisplay port adapter

2. Then, connect the displayport to minidisplay adapter to a thunderbolt 2 to thunderbolt 3 adapter  and then connec that to the LG display

I understand that this is not optimal and using 2 different adapters may very well be a major performance hit, but I'm curious as to HOW much of a performance hit. If I can get 4k resolution out of the monitor as an external display and its the same as an internal display solution or better, that's a major win because that allows me to go through a more streamlined process switching between operating systems. 

 

Thoughts?

 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Yukikaze
(@yukikaze)
Prominent Member Moderator
Joined: 4 years ago
 

I don't think it is going to work at all. Thunderbolt displays expect a thunderbolt input, and those TB to DP adapters are not bidirectional.

Want to output [email protected] out of an old system on the cheap? Read here.
Give your Node Pro a second Thunderbolt3 controller for reliable peripherals by re-using a TB3 dock (~50$).

"Always listen to experts. They'll tell you what can't be done, and why. Then do it."- Robert A. Heinlein, "Time Enough for Love."

 
2012 14" Lenovo Thinkpad T430s [3rd,2C,M] + RX 550 @ 10Gbps-TB1 (Atto Thunderlink) + Win10 [build link]  


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Eightarmedpet
(@eightarmedpet)
Noble Member Moderator
Joined: 4 years ago
 

Have you actually tested your set up or are you in the process of deciding on what to purchase? Because... 

I get 5K in Bootcamp, no one has mentioned this anywhere, everything I read claimed Windows maxed out at 4K on the LG screens, but nope, I have a 5K option.

The performance loss using the LG screen isn't that bad, but from what I read there is little to no loss when using an AMD card due to their drivers being better optimised for eGPUs.

However... I cant for the life of me get round the error 12 I encounter when trying to set up my 570. I have disabled as many other things as possible (as per peoples recommendations) and still no luck. I haven't set up rEFInd or any of this things but its my understanding they do not effect error 12.

 

2017 13" MacBook Pro Touch Bar
GTX1060 + AKiTiO Thunder3 + Win10
GTX1070 + Sonnet Breakaway Box + Win10
GTX1070 + Razer Core V1 + Win10
Vega 56 + Razer Core V1 + macOS + Win10
Vega 56 + Mantiz Venus + macOS + W10

---

LG 5K Ultrafine flickering issue fix

 
2017 13" MacBook Pro [7th,2C,U] + RX 5700 XT @ 32Gbps-TB3 (Mantiz Venus) + macOS 10.15.4 & Win10 2004 [build link]  


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Eightarmedpet
(@eightarmedpet)
Noble Member Moderator
Joined: 4 years ago

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JonRoth
(@jonroth)
Active Member
Joined: 3 years ago
 

@yukikaze I specifically made sure that if the component wasn’t bidirectional, that it would translate the signal in the correct order. In the case of these two adapters, they are both bidirectional. 

@eightarmedpet you get 5k in Windows... whaaat? I only get 4K. I’m jealous! Did you update your thunderbolt drivers? How the heck did you pull 5k off? In regards to the error 12, I’ve read everywhere that AMD graphics are crazy power hungry. It might just be that you need to stick with invidia?

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

.

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Yukikaze
(@yukikaze)
Prominent Member Moderator
Joined: 4 years ago
 

The adapters are bi-directional (mDP to DP obviously is, since it is the same thing in a different scheme), and the TB<-->TB3 adapter works both ways. However, you are NOT using it to convert TB to TB3 or vice versa. What you are doing is trying to convert a DisplayPort output into a Thunderbolt3 input. If the input was USB-C using the DP alternate mode, that might work. But if the input is actually a Thunderbolt3 link, then you need a TB3 on both sides of the connection.

Want to output [email protected] out of an old system on the cheap? Read here.
Give your Node Pro a second Thunderbolt3 controller for reliable peripherals by re-using a TB3 dock (~50$).

"Always listen to experts. They'll tell you what can't be done, and why. Then do it."- Robert A. Heinlein, "Time Enough for Love."

 
2012 14" Lenovo Thinkpad T430s [3rd,2C,M] + RX 550 @ 10Gbps-TB1 (Atto Thunderlink) + Win10 [build link]  


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JonRoth
(@jonroth)
Active Member
Joined: 3 years ago
 

@yukikaze ahhh, I see what you mean. So in terms of trying to get it to function with an eGPU, I’ll have to wait for GPUs to start incorporating thunderbolt 3 out into their Connection outputs?

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

.

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Yukikaze
(@yukikaze)
Prominent Member Moderator
Joined: 4 years ago
 

Yes. And I am not sure how likely that is to ever happen (there were some rumors/announcements, but no products have materialized so far). That said, with official eGPU support on OS X, we might get "Apple Edition" cards at some point with actual TB3 ports.

Want to output [email protected] out of an old system on the cheap? Read here.
Give your Node Pro a second Thunderbolt3 controller for reliable peripherals by re-using a TB3 dock (~50$).

"Always listen to experts. They'll tell you what can't be done, and why. Then do it."- Robert A. Heinlein, "Time Enough for Love."

 
2012 14" Lenovo Thinkpad T430s [3rd,2C,M] + RX 550 @ 10Gbps-TB1 (Atto Thunderlink) + Win10 [build link]  


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