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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
Hello alltogether,
I've got a little question concerning my new display. I would like to have an eGPU to power my LG UltraFine 5K Display and I always thought I need one of those RTX Founders Edition Cards with the USB-C Port to be able to drive it because the display only got a USB-C connector. But can I also use a DisplayPort to USB-C cable to drive the LG? Or is that another kind of signal that the UltraFine can't handle. Because if DisplayPort works, I wouldn't have to get the Founders Edition necessarily! Thanks for your answers!
 

fiatlux

macrumors 6502
Dec 5, 2007
310
62
As far as I know there were two versions of the
LG UltraFine 5K Display: the first could only be driven by a Thunderbolt 3 source, the second one would also accept a USB-C Alternate mode input but only up to 4K.

The USB-C connector on the
RTX Founders Edition Cards does not seem to offer Thunderbolt 3 but Virtualink which seems to be a variation of
Alternate mode, which means it would only work with v2 of the display and only up to 4K.
 
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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
Thanks for your reply! So I have the Version 2 of the LG Display and 4k@60 would be enough for my purpose! So the VirtualLink would work right? But what if I try it with DisplayPort? Has anyone got experience with that?
 
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Crash0veride

macrumors regular
Oct 10, 2016
209
122
Cincinnati
I use the 5k DisplayPort to type-c by moshi. Apple sells it on their site as well. I use it with an eGPU (rx580) and it outputs 5k on Mac and 4K in bootcamp (may work with default bootcamp video drivers but I use others). The downside is you can’t control the monitor brightness or volume with the DisplayPort cable like you could with a typical thunderbolt 3 cable. At least I have not found a way.
 
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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
Thanks CrashOveride for your response! Just got one more question! Does the Thunderbolt solution give you a significant performance loss when using bootcamp?
 
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goMac

Contributor
Apr 15, 2004
7,236
1,218
I use the 5k DisplayPort to type-c by moshi. Apple sells it on their site as well. I use it with an eGPU (rx580) and it outputs 5k on Mac and 4K in bootcamp (may work with default bootcamp video drivers but I use others). The downside is you can’t control the monitor brightness or volume with the DisplayPort cable like you could with a typical thunderbolt 3 cable. At least I have not found a way.

Just a note: In this configuration the Mac is faking the 5k output. It's actually 4k, just with UI scaling. Not actual 5k.
 
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Crash0veride

macrumors regular
Oct 10, 2016
209
122
Cincinnati
Thanks CrashOveride for your response! Just got one more question! Does the Thunderbolt solution give you a significant performance loss when using bootcamp?
I'm not sure where you're anticipating a performance loss. Yes there is a minor performance loss on the eGPU via thunderbolt. I don't think there's any performance loss through the DisplayPort to Usb-C cable in particular. I should have also noted that the Utrafine shows up as 4k in bootcamp with a direct thunderbolt connection as well. This is ver well may be due to the third party drivers, but they're necessary to use an eGPU with a laptop with a discrete GPU.

It's listed as the first 5k cable certified by VESA, but it also seems to imply that this only via usb-c to DisplayPort 1.3/1.4 on the amazon listing. Again, still lets me use full 5k resolution on my Mac (if I wanted, though I choose scaled 2560x1440) via rx580 in sonnet eGPU enclosure. It also shows up as a 5k monitor in system information.
 
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AppelGeenyus

macrumors regular
Nov 3, 2019
118
107
You can only run the LG Ultrafine 5K(even the latest version) at true 5K resolution over Thunderbolt 3. The only eGPU's that currently support this are the two from Blackmagic. You cannot output true 5K from a Displayport on the graphics card to the TB3/USB-C port on the monitor.

Regarding the Moshi USB-C to DP cable, 5K only works one way from USB-C(output device) to DP(monitor) and only if the output device supports 5K output. But in the case of the LG monitor, the USB-C output still needs to be TB3 for real 5K.
 
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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
So I now got a Razer Core X with an RTX 2070 Super Founders Edition. The graphics card is connected to the LG monitor via USB-C and so far it all works fine. But for some reason I have a performance loss of about 20%! Is this normal? Has anyone got experience with this?
[automerge]1582910974[/automerge]
By the way in BootCamp I use a 4K60Hz resolution!
I primarily use the GPU for gaming at 4K!
 
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Crash0veride

macrumors regular
Oct 10, 2016
209
122
Cincinnati
Yes a 20% thunderbolt overhead loss vs an internal GPU is normal. You're basically using a PCIeX4 connection over thunderbolt vs a PCIeX16 on an internal board so there is also theoretically a plateau of performance. I hear after a certain point there the gains become more minimal from nicer cards. That's more just what I've heard, but performance loss over TB3 is a guarantee. See below for some of the OG tests with explanation on the eGPU forum (great resource).

 
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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
Thanks very much for your replies! I appreciate it! So I now got the eGPU and it works really well with BootCamp but the performance loss is quite strong. In 3dmark I get 8300 points instead of 10300! So it is a around a 20% loss!
 
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sprockett

macrumors member
May 19, 2008
58
3
Hi, anyone here managed to get TRUE 5k60hz using DISPLAYPORT (output from graphics card) to USBC on LG5k monitor?

Is it 100% confirmed that graphics will max out at 4k with this method?

I'm considering to get an LG5k monitor to use with my windows PC.

Thanks
 
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HelloAgain16

macrumors member
Original poster
Nov 19, 2019
42
4
Hello sprockett! So for me when going to Windows settings to set the resolution it goes up to 4K but I can't select any resolution higher than that! I'm using an RTX card connected via DisplayPort to USB-C. The cable itself would be able to support 5K60 as far as I know (it's the Moshi bidirectional cable) but I think that the monitor can't work with this signal as it needs a thunderbolt signal in order to work with 5K resolution! I sometime ago watched a Linus Tech Tips video about that topic maybe that can help you to understand more what the LG5K needs as a signal source for 5K!
I hope I could help you!
 
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simacc

macrumors newbie
Aug 29, 2018
17
4
I use the 5k DisplayPort to type-c by moshi. Apple sells it on their site as well. I use it with an eGPU (rx580) and it outputs 5k on Mac and 4K in bootcamp (may work with default bootcamp video drivers but I use others). The downside is you can’t control the monitor brightness or volume with the DisplayPort cable like you could with a typical thunderbolt 3 cable. At least I have not found a way.
Hi, have you tried to use the LG with Displayport adapter with an older computer? Like at 2K...I was thinking I could juggle it between new mac mini and a 5,1 mac pro.
 
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