External Display USB-c Monitor issue

In the second half of the day my problems worsened. Occasionally when unlocking my MacBook after waking it and the monitor both screens would flash pink and the machine would crash and reboot. This happened probably 15 times or so throughout the afternoon as I tested waking my setup with different docks and cables. I’ve yet to experience this without the monitor attached, and also haven’t had it happen again since switching to a DisplayPort cable from my dock to the monitor. The other output problems still persist with the new cable however. We’ll see how tomorrow goes.

When connecting a NEC MultiSync PA322UHD to the Mac Mini M1 (USB-C to DisplayPort with a high-quality, direct cable) I have the same problem, I only get 30Hz (on Big Sur 11.0.1.). My MacBook Pro 2015 does 60Hz over DisplayPort on the same monitor. Apple Support told me to "contact the manufacturer of the monitor to ensure it's compatible". Not very helpful...

I have kind of the same issue. New macbook pro with M1 processor and 34" samsung curved monitor on Big Sur 11.01.

When I plug in my thunderbolt 3 cable the external monitor supports 100 hz. But when I restart my laptop from sleep the system switched my monitor back to 60 hz and I can't select 100 hz anymore. If I then remove the thunderbolt cable and plug it back in the 100 hz is available again.

Looks like some sort of bug.

I give my experience too :

mba M1 + LG 4k via usbc, macOS 11.0.1

Most of the time when I wake up mba from keyboard or mouse, screen doesn't wake up

And sometimes after screen wakes up, resolution is not the one I set (wrongly selected natural resolution), I have to go back to settings and get back to 1440p manually (1440p doesn't have effect at 1st try, have to select an other one and then select 1440p...)

Quit boring

I used LG 49WL95C-W to connect through USB-c cable provide by LG. The connection is OK, and it can wake up by mouse or keyboard after overnight's sleep. So far I am happy. Talk with your display manufacturer to see if they have recommendation.

I agree that it's unacceptable, though I don't regret M1 purchase. I have a similar problem with my Intel Mac Mini, though it usually does not take all day. Restarting computer, restarting monitor, unplugging and plugging the HDMI, that sort of fiddling usually fixes it and it pretty much stays fixed until I need to reboot. It's a serious product issue.

I’m currently having the same issue. The only solution for me is rebooting my MacBook. It seems that sometimes that solves the problem, but it happens very randomly.

I have a MacBook Pro 16 (2019) and a LG QHD (27QN880)

I have the same problem on a 2019 MacBook Pro 16" connected to a Philips Brilliance 346P1CRH display via USB-C.

Since updating to macOS Big Sur 11.1, the display modes are no longer correctly detected. The display is identified as being 38,5-inch (2560 × 1080), even though it is a 34-inch (3440 × 1440) display. Only resolutions up to 2560 × 1080 can be selected in macOS.

I spoke to Apple support during the festive break and have provided the information that I was able to gather on this issue. Since then I have reinstalled Catalina, doing a clean sheet install. No monitor issues are present and I am able to work properly.

@Kimochero - I didn't get issues when sleeping and waking up. I think the monitor issues appear when you unplug your monitor cable and then plug it back in. If you don't need to take your laptop away on some errands, just leave it connected to the monitor like a desktop :)

@Nikitav - I was able to trick 11.1 into showing the full capacity of the monitor by rebooting the MacBook in safe mode and then back into normal mode. But I have a 16" pro, no the the M1, so not sure if this will work for you. Hope it does. Since you are using a desktop, you may be more unlikely to take out the monitor cable out. As far as I have seen, if it starts working, until you reboot or take out the monitor cable - it works.

hopefully 11.2 does some justice to an otherwise nice MacOS 11..

I started having this issue with my LG Ultrafine 4k displays. The primary display connected via Thunderbolt has no issues, however, the secondary display connected via HDMI->DisplayPort->USB-C stopped working AFTER updating to 11.2.

I have opened a ticket with Apple Support, and they are escalating the issue to engineering. I will try to report back with their findings.

Re post: https://discussions.apple.com/thread/252078217?answerId=254525398022#254525398022

I just received a response from Apple Support:

• DisplayPort adapters are NOT supported and NOT INTENDED to work, even if they were working in 11.1.
• The recommended adapters are: HDMI to DVI, then DVI to USB-C.

I am still trying to find a bi-directional DVI <-> USB-C adapter. Can anyone recommend one?

That's all well and good, and I believe you are mostly right. Obviously we are at a disconnect with Apple here, because their engineers are saying we should be using DVI adapters, which won't work.

I would urge everyone that has display issues to call in to Apple Support, and open a ticket, and escalate it until it gets resolved. If Apple engineers don't even know what they are doing, we need to keep bringing this to their attention until they get it sorted out.

I completely agree that the answer from the engineers that I received seems to be a cop-out on their end, and there does not appear to be any interest to address it.

Also, my M1 mini issues may have different causes than others using intel-based Macs in this thread.

I believe what Huuk said above is very true. This is a pretty blatant bug in MacOS. You shouldn't be needing additional ports/ cables/ hubs/ converters/ whatever other junk Apple is constantly pushing our way.. It should WORK OUT OF THE BOX with the CABLE that came with the monitor. The manufacturer that built the monitor most likely certifies that their cables are working with the monitor that you bought. Anything else is pathetic and an embarrassment for Apple. I can't believe an engineer would claim Apple does not support DP. What do they support cucumbers? Now we can't be sure if some people actually don't have any issues with 11.1+ and if there is a hardware issue also with some of the Macs.. We can't be sure what ratio of the people do have issues. But it seems there are quite a lot of us. I personally threw BigSur out the window and went back to Catalina. I can't be bothered to explore workarounds as there is work to be done and finding work arounds is just shoving the problem beneath the carpet. If this is not fixed by apple any time soon I will also happily throw the MacBook in some trashcan and switch to some Surface with WSL2 or whatever else there is that works better, with engineering that actually knows what they are doing..

just my 2cents

Hey Miggl

sorry to hear.. It should work with a USB-C?? Which Mac do you have?

My monitor has DP, USB-C, HDMI, but I use a MacBook Pro 16 with the AMD5300 with a USB-C cable that came with my screen directly. No hubs, no adapters, etc are needed under Catalina. It works 'almost' perfectly. From time to time it loses its scaling or 60hz, but after unplugging/ plugging and switching native to scale it is fixed. I am on the SW271 by BenQ. After upgrading previously to 11.1 all problems appeared. Catalina is quite OK..

Hey @snoop088, I have two LG Ultrafine 4Ks connected. The one connected via Thunderbolt works as expected, never had any issues. But because the M1 only supports 1 external Thunderbolt display, I have to jump around hoops to get the HDMI-out to connect to the USB-C/Thunderbolt-input of the second monitor. :)

The only reason I got mixed up in this thread is because my HDMI => DisplayPort => USB-C solution STOPPED working in 11.2, and others have similar problems with things having stopped working after updating. (Yes, many others had issues since 11.1 as well.) I believe at the core all these issues are related to macOS bugs, but I think the few of us using the HDMI-out port on M1 minis might be able to get a work-around in place until the bugs are fixed.