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LG 5K with MBA

B

badsimian

macrumors 6502
Original poster
Aug 23, 2015
374
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When hooked up to the M1 MBA my LG 5K thinks the default resolution for the display is "Looks like 2048 x 1152" instead of the 2560 x 1440 it should be....when I alt-click on the Scaled button then the top resolution it comes back with is 4096 x 2304 (double the aforementioned looks like default)

So now I am wondering if in fact this MBA is driving the monitor at the correct 5K res or as if it were a 4K screen? I am connecting directly to it via an active Thunderbolt cable.

Screenshot 2020-11-23 at 13.38.27.png
 
Do this command
ioreg -filr -n "dispext0" > ioreg_M1_dispext0.txt

Then find "DPTimingModeId" = in the results. Then in "TimingElements" =, look for the item that has "ID"= that same ModeId. HorizontalAttributes and VerticalAttributes will have the Active pixels of 5120 and 2880 for a 5K output (and "IsSplit" = Yes) "or 4096 and 2304 (with "IsSplit" = No) if it's not 5K.

You many need to try disconnecting and reconnecting the display to get 5K back. Maybe try a different port.
 
badsimian said:
When hooked up to the M1 MBA my LG 5K thinks the default resolution for the display is "Looks like 2048 x 1152" instead of the 2560 x 1440 it should be....when I alt-click on the Scaled button then the top resolution it comes back with is 4096 x 2304 (double the aforementioned looks like default)

So now I am wondering if in fact this MBA is driving the monitor at the correct 5K res or as if it were a 4K screen? I am connecting directly to it via an active Thunderbolt cable.

View attachment 1677565
Click to expand...
Do you have the older or newer LG UltraFine 5K? I have the newer one and don’t have this issue. On another thread, a poster said that unplugging and re-plugging into the other port helped.
 
Just came home with my M1 MBA. Connected my 32" 4K LG monitor. Was blurry so I opened the settings:

3360 x 1890 was missing (this is what I used on my 15" MBP). After some searching in the display information, my Mac recognises it as 27" instead of 32". Maybe that's why the correct options are missing.

Can you check if the display size is recognised correctly? Via About this Mac => Display.

This is what I'm seeing:
 

Attachments

  • Screenshot 2020-11-23 at 20.24.41.png
    Screenshot 2020-11-23 at 20.24.41.png
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It was showing a resolution of 4096, I rebooted and unplugged/plugged in a couple of times and now showing as 5K. Seems twitchy.
 
Mine shows a 4096x2304 resolution as well for the LG UltraFine 5K. Very strange.
 
Last edited:
KPOM said:
Do you have the older or newer LG UltraFine 5K? I have the newer one and don’t have this issue. On another thread, a poster said that unplugging and re-plugging into the other port helped.
Click to expand...
Mine is the older one. Seems a bit random as to what it detects it as.
 
Having the same issue on my Mac mini. After waking from sleep defaults to 4k as standard. Reboot brings it back to 5k. I have the newest LG 5k. (not 1st get)
 
I have both a Gen 1 and a Gen 2. My Gen 1 shows up as 4096x2304 and my Gen 2 shows up as 5120x2880. I'll have to investigate with the reboot to see if that fixes my Gen 1
 
badsimian said:
When hooked up to the M1 MBA my LG 5K thinks the default resolution for the display is "Looks like 2048 x 1152" instead of the 2560 x 1440 it should be....when I alt-click on the Scaled button then the top resolution it comes back with is 4096 x 2304 (double the aforementioned looks like default)

So now I am wondering if in fact this MBA is driving the monitor at the correct 5K res or as if it were a 4K screen? I am connecting directly to it via an active Thunderbolt cable.

View attachment 1677565
Click to expand...
I had this exact same issue. I solved it by resetting the SMC. https://support.apple.com/en-ca/HT201295
 
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MGLXP said:
Did you try resetting the SMC, then going to Display under System Preferences and re-toggling Default for Display under Resolution?
Click to expand...
I did both of those things. Then I updated to 11.01 and now the resolution for Gen 1 is correct.
 
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.

I don't believe you can reset the SMC on the M1...
 
nativeneil said:
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.

I don't believe you can reset the SMC on the M1...
Click to expand...

I have downloaded and installed the 11.1 beta and it seems pretty much to recognise each time now.
 
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