Mac Mini (M1) dual display doesn't work.

I'm enjoying my Mac mini with the M1 soc but unfortunately connecting two monitors does not work. Upon fresh boot, both monitors display correctly on login screen. However, when logging in, both monitors start flickering (see video). I have to disconnect and reconnect one hdmi cable for displays to work again. I currently have one one monitor connected through the HDMI port; the second monitor is connected with a USB-C to HDMI adapter. I should clarify that both monitors work perfectly on their own; the issues come when both are connected. Any ideas?

I've liked a video of flickering. The apps are non-responsive when flickering is occurring.

Mac mini 2018 or later

Posted on Nov 20, 2020 8:09 PM

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chgough54

Level 1

4 points

Posted on Nov 25, 2020 12:44 AM

I have two Samsung QLED 28" monitors - connected them both to the M1 Mac mini and experienced the same problem on start up - persistent flickering. One monitor is connected via an HDMI to HDMI cable - the other connected via an HDMI - USB-C cable. If I disconnected the HDMI - HDMI monitor - the mini would boot normally i.e. the HDMI - USB-C was the only one connected on boot. If I then proceeded to connect the HDMI - HDMI monitor after boot - both monitors worked correctly.

I disconnected both HDMI connections from the monitors and swapped them i.e. leaving the connections into the mini in place and just swapping the HDMI 'ends' of the cables between the two monitors.

Now, the mini boots correctly with both monitors attached. I don't know why that worked - but it was my experience.

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380 replies

Nov 22, 2020 10:38 AM in response to whatisdeadmayneverdie

I have exactly the same issue (and I think the same monitors) as you. It worked great for the first couple of hours but now, not so great.

hcsitas

Level 6

13,964 points

Nov 23, 2020 8:30 AM in response to edinawebguy

Sorry to hear. Well, try disabling sleep, nothing to lose.

hcsitas

Level 6

13,964 points

Nov 23, 2020 8:41 AM in response to pmiles

“Not the M1 Macs but possibly all”

Nope, not a hiccup on my pre-M1 Big Sur. Good luck anyways.

Nov 23, 2020 7:20 PM in response to BillyBrown301

No way that’s awesome!!!

I will try it with a display port adapter that arrives next week. I will update when I try it but this is great news! Thanks for the update!

Nov 24, 2020 5:55 AM in response to Highbury_

Same here. UCB-C to DisplayPort does not work. For me, USB-C alone also does not work, HDMI-only is the one configuration that gets me any display.

Nov 24, 2020 8:37 AM in response to Highbury_

That’s really unfortunate. I was hoping my USB C to display port adapter that’s in the way would work. Hmmm....

Nov 26, 2020 9:48 AM in response to kimac

When you change the refresh rate to fix, do the monitors display correctly after reboot or do you have to modify refresh rate each time?

Nov 28, 2020 11:10 AM in response to kimac

Can be thunderbolt to anything that compliant with your monitor output.

The advice is to use the 2 thunderbolt (usb-C) output on the Mac mini

kimac

Level 1

25 points

Nov 30, 2020 9:24 AM in response to whatisdeadmayneverdie

talking with senior support today..seems like the culprit is these usb c to HDMI adapters...not supported as of now...however I can make it work by toggling the refresh rate

Dec 12, 2020 8:54 AM in response to whatisdeadmayneverdie

Solution: It's the HDMI cable. I swapped it out with my spare MTW 4K HDMI cables and the flickering stops.

Dec 13, 2020 11:34 PM in response to 1HungLo

Yes it does work, with both resolutions, I have tested (3840x2160) by the way I had to buy a better quality HDMI cable which can support 4K.

Dec 14, 2020 8:36 AM in response to MichelCMorel001

No need for a developer account. Just enroll your device in the public beta program and once your download their tool, the update will become available.

macrojd

Level 1

13 points

Dec 14, 2020 5:08 PM in response to GunWanderer

Awesome! BigSur 11.1 solved my issue. No flickering and the configuration of both monitors remain after restarting. Thanks solussd for letting me know. I'm a happy camper today :-)

bt017

Level 1

5 points

Dec 19, 2020 11:28 AM in response to bt017

On step 3b before, your file will have a string of text instead of "XXXX"

solussd

Level 1

4 points

Dec 29, 2020 7:14 AM in response to msct-m1

11.1 made the flicker, not recognize hdmi, and turn off issue better for me, but it’d still happen half the time.

I replaced my hdmi cable with one supporting HDMI 2.1 / 8K and it works flawlessly.

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Mac Mini (M1) dual display doesn't work.