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

Question

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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Answer 1

Top-ranking reply

taro0922

Level 1

4 points

Nov 21, 2020 11:45 PM in response to whatisdeadmayneverdie

Exact same issue here with my new M1 Silicon Mac Mini. I uninstalled and reinstalled the latest OS ver 11.0.1 but didn't solve. I am uploading a video showing the issues:

https://drive.google.com/file/d/19DXVkPxUVI6wt4f-7Qx_fc_1_xfddXOZ/view?usp=sharing

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Answer 2

Nov 22, 2020 12:51 AM in response to whatisdeadmayneverdie

I have the same issue on my M1 Mac Mini too. I'm connecting using an HDMI cable for one screen and USB-C to HDMI cable on the other. Both screens work perfectly fine until I log back in after a reboot, sleep or shutdown.

As soon as I log back in, both screens flicker. Sometimes the screens have swapped positions too, with the background image changing on one screen and the refresh rate changed from 144Hz to 60Hz. The menu bar is still visible and I can get to System Preferences so that I can 'reset' the screens by changing their properties back to how I had them setup originally.

If I use only one screen, there doesn't seem to be an issue either with the HDMI cable or USB-C to HDMI cable.

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Answer 3

Nov 22, 2020 4:54 AM in response to whatisdeadmayneverdie

FWIW, if any of the displays have a Display Port input,

get a USB-C to DisplayPort adapter or USB-C to DisplayPort cable

and connect with a DisplayPort cable.

https://www.amazon.com/s?k=usb-c+to+displayport&crid=12E2A10YXV6AC&sprefix=USB-C+to+%2Caps%2C171&ref=nb_sb_ss_ts-a-p_6_9

Over the years there have been numerous issues with connecting MacMinis

to the non-HDMI ports with any HDMI adapter. One would thing that may

have been solved by now, but perhaps not.

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Answer 4

Nov 22, 2020 8:47 AM in response to woodmeister50

Thanks for the suggestion. I will try this. Might be a couple of days since I first have to order it and wait for adapter to arrive. Both my monitors have a Display Port port so will give it a try. At first I thought I had a defective Mini but given others are having same issue then it’s probably a support problem. We’ll see.

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Answer 5

Nov 22, 2020 8:50 AM in response to taro0922

That’s exactly what happens to me. Mmm...someone below suggested trying a USB-C to Display Port instead of HDMI so I may be able to try that next. Let me know if you find a solution. Pretty disappointing this happens on the new Mac Minis. Other than this issue the Mac is working great.

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Answer 6

Nov 22, 2020 10:58 AM in response to BillyBrown301

Usually when I get the flicker I have to do the following:

I disconnect the USB-C adapter and only connect one monitor through the HDMI port. (No USB-C should be connected to any of the ports).
I reboot and login to the system (only one monitor connected)
Once logged in, everything should be working fine with one monitor
I connect the second monitor by plugging the USB-C connector.
The second monitor should display fine and both should work until next time you reboot or put Mac to sleep.

*if this doesn't work, then I do the exact sequence but starting with the USB-C instead of the HDMI.

Sucks this is happening to us. I'm still not sure if it is a Mac issue or adapter issue.

Earlier today I noticed this on the Mac mini specs page:

Simultaneously supports up to two displays:

One display with up to 6K resolution at 60Hz connected via Thunderbolt and one display with up to 4K resolution at 60Hz connected via HDMI 2.0

Thunderbolt 3 digital video output supports

Native DisplayPort output over USB‑C

Thunderbolt 2, DVI, and VGA output supported using adapters (sold separately)

HDMI 2.0 display video output

Support for one display with up to 4K resolution at 60Hz

DVI output using HDMI to DVI Adapter (sold separately)

https://www.apple.com/mac-mini/specs/

So maybe Mac mini doesn't support connecting two displays via HDMI, maybe one has to be Display Port as the specs do list it as supporting 'Native DisplayPort output over USB‑C".

I'll ponder about buying a USB-C to Display Port adapter to try.

For now I'm just using one monitor since I don't want to be disconnecting/connecting cables each day...

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Answer 7

Nov 22, 2020 11:02 AM in response to whatisdeadmayneverdie

Yes - that mirrors exactly my issues too and ways to resolve them. A bit frustrating - especially how good the rest of the machine is! My monitor only has HDMI and so I’m not 100% sure of next steps...

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Answer 8

pmiles

Level 6

16,054 points

Nov 23, 2020 8:35 AM in response to whatisdeadmayneverdie

Just a shot in the dark here, but several have reported that Big Sur 11.0 broke HDMI support on the 2018 Mac mini (previous setup worked under Catalina). One user said that upgrading to Big Sur 11.1.0 beta fixed the problem. Not the M1 Macs but possibly all this is a Big Sur issue.

Not advocating that you update to a beta version since there is a risk of not being able to downgrade back. Just something to ponder.

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Answer 9

Nov 23, 2020 5:51 PM in response to whatisdeadmayneverdie

Quick update: got a USB-C to VGA cable and both monitors work with no flickering or issue. It would seem it is the second HDMI that causes the problems. I didn’t have a monitor with a DisplayPort so I couldn’t test that. But VGA works no problem!

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Answer 10

Nov 24, 2020 3:46 AM in response to whatisdeadmayneverdie

I thought I'd give the idea of trying a USB-C to DisplayPort cable a try as well so I went out today and got one. But... No luck. Exact same issue with the screens flicking as if I was still using the USB-C to HDMI cable.

Also, if I swap the USB-C to DisplayPort cable to the other USB-C port, the whole OS just seems to lock up completely until I pull both the HDMI and USB-C cables out and put only one back in.

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Answer 11

Nov 24, 2020 8:39 AM in response to pete_stmarie

Wow that’s interesting. Now I’m starting to wonder if it has to do with the type of cable we use or the type of monitor. My monitors aren’t 4K , they’re simply 1080 with 60hz refresh rate. This one gets me one display either with hdmi or usb c-to-hdmi adapter.

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Answer 12

pmiles

Level 6

16,054 points

Nov 24, 2020 9:03 AM in response to whatisdeadmayneverdie

People might find the information in this link helpful (talks about cables and specs):

https://blog.startech.com/post/tech-talk-display-technologies/

Might offer some help in deciding what adapter or cable to try for your specific monitor needs.

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Answer 13

rdf7777

Level 1

8 points

Nov 24, 2020 11:27 AM in response to whatisdeadmayneverdie

Hi, I have m1 mac mini, 8gb ram too and for the first week I used USB-C to mini-display port adapter with an old 24" Apple Cinema Display no problems. Had another cinema display in storage, it works fine with my 2015 MBP 13" Retina but will not work on Mac Mini plugged into the HDMI to Mini-Display port adapter I bought. When I have both plugged in it's recognizing there should be a second display to the right, but it won't light up?

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Answer 14

Tnt7982

Level 1

4 points

Nov 24, 2020 9:49 PM in response to whatisdeadmayneverdie

I finally got the M1 Mac mini to work with dual screens . One monitor pulled in to hdmi and the second into the thunderbolt 3 slot using a hdmi to thunderbolt three adapter . I was using a non thunderbolt 3 adapter and that caused my issue:

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Answer 15

Tnt7982

Level 1

4 points

Nov 24, 2020 10:24 PM in response to whatisdeadmayneverdie

No sir rebooted three times and wake/ sleep three times.

running 2 asus 27 inch 2k monitors via hdmi for one and hdmi to thunderbolt 3 for the other.

no issues two days in. Hopefully Apple will figure this out for everyone and stop this madness no matter what setup you have.

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

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