eGPU to LG 24" Ultrafine 4k, possible?

LiE_

macrumors 6502a
Original poster
Mar 23, 2013
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Is there a way to connect an eGPU to my LG Ultrafine 24" 4k (the new one) ? It has 2 TB3 and 3 USB-C connections. All GPUs have HDMI or DisplayPort, which obviously can't directly connect to the monitor. Would a DP to USB-C cable work to drive the monitor from the eGPU?
 

manuelg

macrumors newbie
Feb 1, 2019
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You may want to try the Moshi USB-C to DisplayPort Cable. As far as I know, it is the only one with bi-directional support.
 

LiE_

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Original poster
Mar 23, 2013
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You may want to try the Moshi USB-C to DisplayPort Cable. As far as I know, it is the only one with bi-directional support.
That does look interesting. It’s a shame I can’t find any mention of it being used in the way I intend. It would be impossible for me to test without buying an eGPU.
 

Stephen.R

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Nov 2, 2018
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You may want to try the Moshi USB-C to DisplayPort Cable. As far as I know, it is the only one with bi-directional support.
The problem I think, is that the display's input is not USB-C (e.g. a number of displays have "USB-C in" which is effectively just using the DP Alt-Mode of the USB-C connector, and thus should work with that part), it's TB3. Same connector, different protocol, and I would be very surprised if it worked - at best you'd get video but the downstream USB-C ports would be either useless, or crippled to USB 2.0 speeds)
 

LiE_

macrumors 6502a
Original poster
Mar 23, 2013
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The problem I think, is that the display's input is not USB-C (e.g. a number of displays have "USB-C in" which is effectively just using the DP Alt-Mode of the USB-C connector, and thus should work with that part), it's TB3. Same connector, different protocol, and I would be very surprised if it worked - at best you'd get video but the downstream USB-C ports would be either useless, or crippled to USB 2.0 speeds)
I was under the impression that the input is both USB-C and TB3 over USB-C. This allows the iPad to connect.

Also on Apple website under highlights it says:

Video, data and power over a single Thunderbolt 3 (USB-C) cable (included) or USB-C cable (included)
Either way, thinking about it, it won't work properly. The DisplayPort on a GPU isn't designed to carry USB functionality so it would loose that even if the display was output.

I'll have to hold out hope that AMD release a Navi card with the VirtualLink connection (USB-C) and Apple support the GPU. The spec has support for VirtualLink, but none of the current board partners have put a USB-C output on the GPUs.
 

Stephen.R

macrumors 68000
Nov 2, 2018
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I was under the impression that the input is both USB-C and TB3 over USB-C. This allows the iPad to connect.
Ah, ok I missed that part, so yes, the video part would probably work then.

The DisplayPort on a GPU isn't designed to carry USB functionality so it would loose that even if the display was output.

Yep, definitely.

I'll have to hold out hope that AMD release a Navi card with the VirtualLink connection (USB-C) and Apple support the GPU.
The Blackmagic eGPU would work now, and in theory any other (macOS supported) card with TB3 out would work too - but given that most results for "AMD GPU TB3" refer to cards in eGPUs, I'm not finding anything quickly that does support it.
 

LiE_

macrumors 6502a
Original poster
Mar 23, 2013
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I did a bit more digging and it looks like there is a cable (Huawei VR2 cable) that should allow both display and USB (not fast USB but enough for audio and brightness control) to the LG 4K.

https://egpu.io/forums/gpu-monitor-peripherals/easiest-way-to-drive-lg-ultrafine-4k-monitor-with-egpu/

It's not a cheap cable.

https://www.ebay.co.uk/itm/100-Original-Huawei-VR-2-Computer-Connection-Cable-DP1-2-USB2-0-to-Type-C-Cable/333267668172

I'll have to give it some thought.
£260 Razer Core X
£380 Vega64
£60 Huawei VR2 cable
£700 Total

So not cheap, but likely a better solution than building a separate PC for playing some games. Other factors to take into consideration are noise from the eGPU and the performance hit running an eGPU.
 

LiE_

macrumors 6502a
Original poster
Mar 23, 2013
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Update time. I bought the Razer Core X, a 5700 XT and the Huawei VR 2 cable.



So I have my Huawei VR 2 cable and I thought it may be useful to document how to use it, based on my testing. I couldn't find this info else where so others might find it interesting.

macOS Usage

- You cannot boot into macOS with the eGPU connected using this cable, you get no display. Unplug the eGPU from the Mac mini when booting into macOS.

- You should instead boot with the standard Mac mini > LG UltraFine TB3 connection.

- When macOS has loaded, unplug the Mac mini > LG UltraFine TB3 connection and plug in the eGPU. The eGPU will come to life and after a few seconds you'll have full display and brightness controls.

- Waking from sleep is fine with the eGPU connected.




Windows Bootcamp Usage

- Windows requires the eGPU to be connected when booting. However you do not get the boot loader with the eGPU connected, so you cannot select which OS to boot.

- To work around this, you should set Windows as the default OS when turning on your Mac mini.

- This allows you to reboot in macOS with the eGPU connected, and go into Windows bootcamp without having to do any unplugs.

Benchmark





Things to test

- What I haven't tested yet is if I switch the eGPU off at the power while the Mac mini is asleep, but then switch it back on and wake it up does it output to the display.