External Display flickering on M1 MacBook Pro

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Level 1

36 points

External Display flickering on M1 MacBook Pro

Hi,

I have:

M1 MacBook Pro (1tb, 16gb)
Dell S2721QS external display (capable of 4K at 60hz)

I first connected this display using HDMI, however my Apple adapter only supported HDMI 1.4b, so it only supported 4K at 30hz. I then switched to a USB-C to DisplayPort cable, and the screen worked great.

However, not, if my Mac locks, and I wake it up again, the screen sometimes starts flickering. On for 2 seconds, off for 1 second, roughly that pattern. I have to unplug the display from power most of the time, and reconnect. But then if the Mac goes to sleep again, I risk seeing the same flickering.

One thing to note, I hav tried the two different USB-C ports, no change in issue. I can also see that in ColorSync Utility, the Dell display has a HDMI HD and HDMI SD profile, but not a DisplayPort one?

Do I need to reset SMC (is that even possible on Apple Silicon) or what do I do to get the Mac to forget all external displays it remembers, and instead treat this display as a fresh new external display?

MacBook Pro 13″, macOS 11.0

Posted on Dec 13, 2020 10:16 PM

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Answer 1

Feb 5, 2021 3:25 PM in response to SingingApple

I having the same problems with my MacBookAir with the M1. I have the same monitor you do and I'm using the USB C to DisplayPort cable found on the apple store website. I have updated to 11.2 and the problem is still here. I can get this to work fine if I plug the monitor into the Mac while the monitor is powered off (if its sleeping the monitor will flash). Or another way to get it to work is to unplug and replug it back in twice.

Is the HDMI method you talked about still working? Is that odd yellow problem still there after updating to 11.2?

I did just get off the phone with Apple support with an extremely helpful gentlemen. He thinks its a software glitch that may be hopeful fixed in upcoming updates.

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Answer 2

SingingApple Author

Level 1

36 points

Dec 28, 2020 2:41 AM in response to amos114

I failed to find a solution. In the meantime, I ordered a new Apple USB-C Digital AV Multiport Adapter and connected the display via HDMI. Specifically, you have to order the latest version of the adapter to make sure it supports 4K at 60hz via HDMI. It also gives you an additional USB-C charging port and a USB-A port, which is nice. But it's a bit expensive.

With this setup, I no longer get the flickering issue. So it seems like it's flickering only when connected via DisplayPort. But now I have this occasional issue where, once the Mac goes to sleep, when it wakes up the screen can be extremely yellow. I think this is a True Tone bug, possibly. But restarting the display fixes that problem.

These seem to be issues with the M1 Macs in general and the new architecture. Hopefully future macOS releases and future hardware releases solve these problems.

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Answer 3

Feb 16, 2021 3:45 PM in response to SingingApple

I was able to find what is causing this problem. After much looking it seems the M1 Macs don't like DisplayPort at 60Hz. I was able to find some YouTube videos of 60Hz not even being an options for DisplayPort. This seemed to affect everyone no matter if you where using a dock, USB-C to DP cable and brand of monitor. (Here is the video I found of the his Mac not even giving him a 60Hz option - https://youtu.be/mbPa5f1lcqo )

How I was able to confirm my fix was after plugging the monitor in and with it blinking. By changing the display to 30Hz the blinking stops. As I write this I was able to change it back to 60Hz and its still working but it seems to be very fragile at 60Hz.

I'm going to be switching to HDMI as trying to get this DisplayPort cable working every time is getting worse every day. I wish Apple would fix this and I will be submitting this feedback to Apple and I hope one day its fixed with an update. I strongly encourage everyone with this 60Hz problem to submit that problem to Apple here https://www.apple.com/feedback/

Apple does take the time to read everything sent to them and this how they are informed about problems.

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Answer 4

BK_yyj

Level 1

4 points

Dec 28, 2020 3:53 PM in response to SingingApple

I have the same setup with the MBP M1(16/1T) with the Dell S2721QS. I'm using a CalDigit TS3+ dock. The problem didn't seem to show up for the first couple days.

If I select "Default for display" the screen blanks faster than when I select Scaled.

Don't know if its related but I also see

"error 15:52:40.028527-0800 kernel Failed to write key 1950826800 to SMC with error code 86" in the logs

Running 11.1

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Answer 5

SingingApple Author

Level 1

36 points

Feb 5, 2021 4:13 PM in response to cowtown1875

Hey mate,

The HDMI method still works, haven’t had the issue. However, the yellowing thing is still there, but I’m pretty sure it’s a macOS bug, because it corrects itself when I resize a window or just reload a tab etc.

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Answer 6

Mar 10, 2021 5:12 AM in response to cowtown1875

This is also a problem using VGA monitors.

I'm using a 16-inch MBP from 2019 running Catalina 10.15.7 with a pair of Dell E2213 monitors with USB-C to VGA adapters as extended displays.

Coming out of sleep, it takes forever for all 3 monitors to "settle down". The displays (including the laptop) get cycled through flashing on and off for a while. After 5-10 minutes the displays stabilize and the computer becomes usable.

I have also noticed I can speed things up by unplugging the USB-C cables for the external monitors and connecting them again one at a time. Same flashing occurs, but it settles down a lot faster.

I'm kind of disappointed with my experience so far. This is my first experience using a Mac, it's the default developer machine provided by my new employer. I have never experienced anything like this will Dell Windows 7 and Windows 10 machines. I expect better of Apple.

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Answer 7

Mar 10, 2021 8:14 AM in response to slackerjack1943

I would stop using VGA. Thats an old analog monitor connection that's is not used anymore. I suspect there is a problem with the translation from digital (USB C) to analog (VGA). I would try DVI as that monitor should have that connection. If that does not work I would try the following

1st - New or different brand of cable

2nd - Update to Big Sur

After switching to HDMI my problems are gone. When I used Intel Macs in the past they really like digital monitor cables vs analog.

Intel might be the problem on this issue not Apple. As MBP 16 have both Intel and AMD graphics cards one of these are more than likely the problem. Since Intel in the last 6 years has just coasted and become the laughing stock in the computer community I would throw them under the bus. There is a reason companies like Apple and Microsoft are leaving Intel.

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