Level 1

21 points

M1 Mini issue with LG 27" 5K Monitor

I have a new M1 Mini running the LG 5K monitor from they Apple store. The monitor is recognized with the 5120 x 2880 resolution spec on boot or monitor reset (unplug and reinsert thunderbolt cable), but invariably falls back to a 3840 x 2160 resolution when the monitor goes into screen saver or sleep.

Three different thunderbolt cables have be used, a second LG Monitor tried, and have tried both Thunderbolt ports on the mini. A replacement Mac mini seems to be the last resort, but I feel this may be a bigger issue affecting others, and that a replacement will not fix this.

Is anyone running this monitor with Big Sur or ideally with the M1 Mini?

Posted on Dec 11, 2020 5:36 PM

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Chris Wilhoite

Level 1

9 points

Posted on Jan 17, 2021 6:39 PM

thoughts,

I called Apple Saturday and started a case. Talked to a senior tech person for a while. Went over everything. Told her about these threads in the forum. She had me set the energy saver to never. Thinking that this would push it to occur. The interesting thing is since changing it, it has never occurred. Makes me think that going into sleep may be what is causing it. WHY, I do not know.

I did see that there are 3 threads about this and on one someone mentioned they could make it happen by setting a hot corner to sleep monitor.

She also wanted me to try using the USB-C cable supplied by LG and see if it still happens. Have not tried that yet as I am seeing how long it will go without messing up by sleeping monitor being set to never.

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100 replies

Mar 16, 2021 1:51 PM in response to K9x3

go to the LG US website and scroll through software and drivers for your model, you want to download the most recent mac version of "On Screen Control"

Jan 13, 2021 6:23 AM in response to K9x3

So, I have 2 of these monitors and have the issue on three separate machines (same monitors) a 16" MacBook Pro with 11.1, M1 MacBook Air, M1 Mac Mini. I don't think it's related to just the M1 architecture. It's annoying though. I just unplug and plug it back in and it goes away.

K9x3 Author

Level 1

21 points

Jan 18, 2021 3:36 PM in response to Ross Ellingson

Ross, I tried this and my monitor fell back to a 4K resolution, which is perhaps why you haven't seen the issue. As a 4K monitor, I believe there is only one video signal sent, so the issue doesn't happen. If I understand correctly, to have the 5k resolution, two display signals are sent ** the host.

Before the Big Sur update to 11.1, my monitor would initially be seen as a 5K monitor, but it would eventually fall back to 4K. If I left it alone, it operated fine that way without the pixel shift.

When I reinserted the TB3 cable, the monitor returned to 5K (5120 x 2880). Check your resolution to see if you got 4K or 5K. My guess is that the USB-C cable is for devices that can only render 4K, whereas the TB3 cable has the bandwidth to render up to 6K with compatible hosts.

Best Regards,

Jon

Jan 26, 2021 10:32 PM in response to K9x3

I do have this issue with my MBP 16" 2019 on Catalina 10.15.7 and connect to LG 5K Monitor(27MK5KL-B)

Have you guys checked which firmware that you have in the monitor?

I reached the LG support for this, will update this soon.

K9x3 Author

Level 1

21 points

Feb 9, 2021 7:33 AM in response to lormov

Yes, system report confirms the TB3 spec up to 40gb/s. I've tried many combinations of the ports and four different cables. I'm convinced it is an issue either with the monitor or operating system in the way it processes two display streams. You'll notice in the system report for the display, the UI looks like 2560 x 1440, and this times two gives you the 5K spec for the monitor.

What I don't understand is why the pixel shift wouldn't then happen on a 5K iMac, unless the issue is within the TB3 interface -- creating an issue only for external 5K TB3 displays.

K9x3 Author

Level 1

21 points

Apr 14, 2021 10:09 AM in response to Holger Laufenberg

Holger,

I understand and share in your frustration. I have been on the phone with LG several time after opening a case with them, and it is going nowhere after a year. If the distortion you are referring to is the pixel shift issue described in the thread, there was one contributor who experienced this same issue on a laptop running Catalina.

You can reduce some of the hassle of resetting your monitor by using hot spot corners and setup one to put your monitor to sleep. Using the hotspot will usually resolve the issue in one or two attempts vice unplugging cables.

I was unaware of LG rolling back a firmware update, but LG has been the least forthcoming in addressing the issue. I have heard Apple is working on building their own line of monitors again, and that may become the solution for future purchases that avoid the finger pointing.

The challenge then is what to do with the premium priced LG 5K monitor that is built for Apple users but doesn't play well with their Apple hardware.

Thanks for the post.

Apr 26, 2021 2:49 PM in response to K9x3

Today Apple released Big Sur 11.3. It did NOT include a fix for the pixel shift. LG has made it clear that they can't and won't resolve this issue - as the monitor is no longer in production and they generally don't care about a small amount of Apple users running Big Sur on M1 computers with this outdated display. Thus Apple was the only hope to get this resolved. But because its a 3rd party display, Apple really doesn't care all that much either - despite it being the only 3rd party display actively promoted and sold directly by Apple. Unfortunately, the April 20th event did not offer a solution. I was hoping Apple would launch an affordable display again or launch a new higher-end iMac. The 24" TikTok-Mac it released instead isn't doing it for anyone except...well the TikTok generation using it for well what those kids do . So It seems we gotta just deal with the distortion until Apple releases a 27+" iMac or an affordable Display.

lormov

Level 1

4 points

Feb 8, 2021 12:04 PM in response to mstrshikadance

Dis you check if the thunderbold cable is supported with 40gb/s in the system report?

K9x3 Author

Level 1

21 points

Jan 16, 2021 8:35 AM in response to Chris Wilhoite

Hi Chris, I have tried numerous cables, including Apple brand, and the issue occurs with all of them. The 11.1 update fixed a specific issue with the LG monitor not being seen a 5K monitor, with the fix specifically listed within the update. I was also having that issue, and the fix indeed corrected it.

There was one user in the thread that reported the pixel shift issue from an intel MacBook Pro in the prior Catalina OS and the Big Sur update. I'm on the second LG 5k monitor, so I'm inclined to believe the issue is in the software. I've had zero luck with LG in determining what is the latest firmware version for the monitor is after multiple calls -- their answer is always send it in for testing and repairs.

The timing wasn't right for me to wait for an Apple Silicon iMac, so I have what I have at this point in time and will hope enough noise online will generate a fix.

Thank you for the response

Jan 18, 2021 10:20 AM in response to Chris Wilhoite

It’s been several days since switching to the supplied usb-c cable and no pixel shifting band to be seen. I think most that tried a different cable just swapped for another thunderbolt 3 cable and dismissed it could be the cable spec.

Jan 18, 2021 4:14 PM in response to Ross Ellingson

The majority of these reports are of M1 Macs. There are also a few people with intel macs, but are those first generation or second generation LG 5K monitors? That's important. The second generation of LG 5K monitors solved the problems that I had with my 16" Macbook Pro but still lead to the pixel shifting problems with the M1 Silicon.

Jan 23, 2021 12:58 PM in response to K9x3

I probably shouldn't say this, but I switched out for the USB-C cable for a day or two. Then I put the Thunderbolt 3 cable back on. I've gone about 6 days and have not had it reoccur, and that is with having the monitor 'Sleep', I'll take it. Who knows but assuming it will be fixed it an update.

Feb 18, 2021 7:02 PM in response to K9x3

I have this problem on the M1 Mini with LG 27” 5K monitor as well. The pixel shift doesn’t show up in the screenshot. However, that still may not be a monitor issue. I could see the issue only occurring after the GPU does the downscaling of the image from 5K to 2560x1440 and sends it off to the monitor. If the GPU does the downscaling on the fly—reads frame buffer in memory (which is correct) but then creates the error in the stream that is sent to the monitor.

I hope this is it, then it’s software, not my expensive monitor . . .

K9x3 Author

Level 1

21 points

Apr 14, 2021 10:58 AM in response to Holger Laufenberg

I'm curious what LG said on the issue, as I've never got that far. I understand the panels in this monitor are same/similar to those in the 5k iMac, but yet I've not heard of this issue with the iMac. This leads me to believe the Thunderbolt interface is introducing the issue with the external monitor if the panels are the same.

Thanks for your persistence in getting much further than I have with LG, and I'd like to know more. It would seem to me that if LG is not fixing it, they believe the issue is with Apple. With Apple, I went through months of trial and error with a Tier 3 tech, and even received a new Mac mini to no avail and was left hoping a software update would fix the issue.

MEADEN

Level 1

15 points

Jan 18, 2021 5:49 PM in response to Chris Wilhoite

Check the model number: 27MD5KA is the 1st Gen, and 27MD5KL is the 2nd Gen.

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M1 Mini issue with LG 27" 5K Monitor