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jacol

macrumors newbie
Original poster
Nov 19, 2020
1
2
Hi,

can anyone, having mentioned devices at hand, please confirm whether M1 macs work (support all features - full 5k resolution, usb-c hub, webcam ...) with a previous version of LG 5K Ultrafine display (27MD5KA-B)?

Thanks.
 
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badsimian

macrumors 6502
Aug 23, 2015
302
125
 

badsimian

macrumors 6502
Aug 23, 2015
302
125
If you go to About this Mac though what does it say? Mine looks like this:-

Screenshot 2020-11-23 at 18.42.30.png
 
Last edited:

badsimian

macrumors 6502
Aug 23, 2015
302
125
Okay there is a thread on this. It looks like it is a little twitchy, often get stuck in 4K and you have to switch the cable into the other port a couple of times. I am back at proper 5K now.

 
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nativeneil

macrumors newbie
Nov 26, 2020
8
0
Anyone managed to reliably fix this? I've got an M1 MacBook Air and the LG Ultrafine 5K 27MD5KA (1st Gen) running 11.0.1 but only displaying as 4k. Multiple reboots and port switches but can't get it to recognise 5k. Also the LG Screen Manager doesn't recognise the monitor.
 

strangeengine

macrumors member
Jan 30, 2017
84
64
Anyone managed to reliably fix this? I've got an M1 MacBook Air and the LG Ultrafine 5K 27MD5KA (1st Gen) running 11.0.1 but only displaying as 4k. Multiple reboots and port switches but can't get it to recognise 5k. Also the LG Screen Manager doesn't recognise the monitor.

Mine comes up in 5K correctly but LG Screen Manager also doesn't see it.
 

dieselm

macrumors regular
Jun 9, 2009
100
41
I had a similar issue. it's probably your cable.

An official apple thunderbolt cable will connect in 5K. A "lesser" usb-c cable connects in 4k. I'm not clear why it even works at all. The first gen LG Ultrafines don't support USB-c display output like the 2nd gen do (like for the iPad).
 
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nativeneil

macrumors newbie
Nov 26, 2020
8
0
I've tried a few cables without success and never had it display as 5k. There is a bug. I wonder if when you change it to run at 2560 x 1440 if that is true retina or if everything is a little off...
Screenshot 2020-11-27 at 09.09.45.png
Screenshot 2020-11-27 at 09.09.55.png
Screenshot 2020-11-27 at 09.10.18.png
 

arfung

macrumors member
Jun 27, 2015
41
19
Hi,

I had issue in which my M1 MBP would only connect to LG 5k ultra fine with 4k resolution. My problem was the cable. TB3 cables actually come in 20Gbps and 40 Gbps. My 20Gbps cable would only drive the monitor at 4k, and when I used a 40 Gbps cable, I could drive the monitor at 5k. Go to "About this Mac" -> "System Report" -> "Thunderbolt" and make sure all of the Thunderbolt connections between computer and monitor are running at 40 Gbps. I have a snapshot below - I'm running through a CalDigit Dock.

Screen Shot 2021-01-08 at 20.42.13.png
 

BobHinden

macrumors member
Nov 11, 2020
69
41
San Francisco Bay Area
I have used my LG 5K display on my M1 MacMini with the cable that came with the monitor and an Apple Thunderbolt 3 cable ($39 on Amazon). I get 5K with either. Currently using the Apple one because it is shorter, not that I think it should make any difference.
 

joevt

Contributor
Jun 21, 2012
3,705
1,787
I've tried a few cables without success and never had it display as 5k. There is a bug. I wonder if when you change it to run at 2560 x 1440 if that is true retina or if everything is a little off...
Check the Thunderbolt section to make sure the display is connected properly like arfung says. It should be:
Code:
Link Status 0x2
Speed: Up to 40 Gb/s x1
Current Link Width: 0x2

If there is a problem, then maybe connecting the display to a Thunderbolt dock might help?
 
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badsimian

macrumors 6502
Aug 23, 2015
302
125
i think 11.1 fixed this. I used to have the issue with an expensive active TB3 cable but it works consistently 100% now
 

toddpeperkorn

macrumors newbie
Mar 19, 2021
5
0
Interesting. I have an M1 MBA and it will only show 2560x1440. Does this mean a problem with the cable, with the monitor, firmware, software, gremlins, or something else?

CleanShot 2021-03-18 at 10.25.57@2x copy .png
 

arfung

macrumors member
Jun 27, 2015
41
19
Interesting. I have an M1 MBA and it will only show 2560x1440. Does this mean a problem with the cable, with the monitor, firmware, software, gremlins, or something else?

View attachment 1746043
I think it's your cable. Are you directly connected from M1 MBA - LG5k? or, are you going through some kind of dock. Here is my sysinfo. As you can see, speed through my cable is much higher...
 

Attachments

  • Screen Shot 2021-03-19 at 13.42.19.png
    Screen Shot 2021-03-19 at 13.42.19.png
    77 KB · Views: 29

toddpeperkorn

macrumors newbie
Mar 19, 2021
5
0
CleanShot 2021-03-18 at 10.25.57@2x copy .png


So that is connecting with the (Amazon) Thunderbolt 3 cable that was included in the box. It was NOT the one that originally shipped with the monitor, as this was a "renewed" monitor from Amazon.

But notice the dramatic difference in the firmware versions.You have firmware version 43.1 and the Link Controller firmware of 1.23.0. My firmware is 9.4 and link controller firmware is 0.14.0.

When I connect using an Apple .8m Thunderbolt 3 cable, it won't' display at all. It won't turn on.

So here's another interesting bit:

I also have a 2018 Mac Mini, and when I connect the LG to THAT using the Apple Cable, it recognizes it at full resolution, etc. So there must be something either in the firmware of the monitor, or in how Big Sur manages graphics with the M1s, that is causing the problem.

Sigh. So do I return it or not? I'm running out of ideas on how to resolve this. There is no way to get a firmware update, from LG, and I can't find anything at Apple support about the problem.
 

arfung

macrumors member
Jun 27, 2015
41
19
That is indeed strange. Is your 2018 mini running same version of MacOS as MBA? I think it should work with the Apple .8m TB3 cable for both. Have you tried shutting down and then powering up the MBA and then connecting to different ports (I'm reaching here, but maybe one port is bad?)
 

joevt

Contributor
Jun 21, 2012
3,705
1,787
View attachment 1746137
So that is connecting with the (Amazon) Thunderbolt 3 cable that was included in the box. It was NOT the one that originally shipped with the monitor, as this was a "renewed" monitor from Amazon.
Only one of the lanes is working (link width x1) so you're only getting 20 Gbps instead of 40 Gbps. Maybe the cable is broken.

But notice the dramatic difference in the firmware versions.You have firmware version 43.1 and the Link Controller firmware of 1.23.0. My firmware is 9.4 and link controller firmware is 0.14.0.
You have a 27MD5KA. Maybe arfung has the second version 27MD5KB which uses a different Thunderbolt controller. Notice his Thunderbolt Device ID is different.

When I connect using an Apple .8m Thunderbolt 3 cable, it won't' display at all. It won't turn on.
What does the Thunderbolt info show in that case? Maybe the cable isn't broken. Maybe the Thunderbolt port of the display is broken.

I also have a 2018 Mac Mini, and when I connect the LG to THAT using the Apple Cable, it recognizes it at full resolution, etc. So there must be something either in the firmware of the monitor, or in how Big Sur manages graphics with the M1s, that is causing the problem.
Maybe there is a problem with the M1 Mac then. You tried both Thunderbolt ports? You tried all orientations of the USB-C connectors (flip them upside down - two orientations per end, four total per cable).

Sigh. So do I return it or not? I'm running out of ideas on how to resolve this. There is no way to get a firmware update, from LG, and I can't find anything at Apple support about the problem.
Do you have a Thunderbolt dock you can try to connect the LG to?
 

toddpeperkorn

macrumors newbie
Mar 19, 2021
5
0
Only one of the lanes is working (link width x1) so you're only getting 20 Gbps instead of 40 Gbps. Maybe the cable is broken.


You have a 27MD5KA. Maybe arfung has the second version 27MD5KB which uses a different Thunderbolt controller. Notice his Thunderbolt Device ID is different.


What does the Thunderbolt info show in that case? Maybe the cable isn't broken. Maybe the Thunderbolt port of the display is broken.


Maybe there is a problem with the M1 Mac then. You tried both Thunderbolt ports? You tried all orientations of the USB-C connectors (flip them upside down - two orientations per end, four total per cable).


Do you have a Thunderbolt dock you can try to connect the LG to?
I spent a lot of time with Apple yesterday on the phone, talking to a senior engineer. He is as baffled as I/we are. They are spending the next several days researching, and then we have a scheduled call for next Wednesday. In the meantime, I'm going to try on Monday to go through LG's tech support and see if I can find out another answer there.
 
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