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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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Posted on Nov 22, 2020 10:58 AM

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...


380 replies

Mar 29, 2021 1:28 PM in response to whatisdeadmayneverdie

Thanks so much! I thought I had a bad Mac Mini -- BUT surprise! We all do! So ... I saw the 'flickering' video - I had that - found a way to get by it ... Here's what I have connected to my 3.2Ghz-6Core Intel i7 with Intel UHD Graphics 630 1536MB - I've no solutions to add to this thread but I wanted to share the same struggles ...


  1. Kamvas Huion 13" 1080p tablet/monitor ... connected into a mini-display port via HDMI to USB-c (not sure the quality of the connector) ... works fine though ...
  2. An old Haier 1080p 40 inch TV also connected into a mini-display port via HDMI to USB-c (again, not the quality of the connector) ... works fine though ...
  3. A newish 4k HiSense TV connected directly to HDMI on the Mac Mini ... works GREAT! - when it works ... (this solved the flickering)


So here are the remaining struggles ... (and I'm running Big Sur 11.2.3) ...


  1. It's a crap shoot as to which monitor becomes my main display on reboot UNLESS I power off both my TVs and boot so that the Kamvas Tablet/Monitor is the only USB device. I think there must be a 'powering up' order for the TVs that might fix this ... No matter, I presently leave the computer on most of the time ... if I let only the monitors go off/dim sleep ... it seems to be aok (NOT the Kamvas) ... when the TVs are turned on ... it's just the Mac Mini that you have to keep alive ALL THE TIME. I 'un-enabled' the power nap option in Energy saver just today - so I'll see what happens ... so the computer doesn't nap - just in case i.e. I've stopped shutting down & restarting my Mac ...
  2. Often ... I lose my 4k TV on start-up - just does not detect it ... so I used to boot / reboot etc. often (not anymore cause I don't turn the computer off).
  3. Now - when the computer and monitors all work together - and they do - I fiddle til they do - yes ... I love my Mac - It's fabulous to have the large screen-scape - I can do all my former dual-display work in just the one 4k TV/monitor ... I deliver my lectures simultaneously using the tablet ... and in the third display I have my mail, calendar, messages etc ... It's really nice when it works ... I'm only a bit frustrated with the fiddling I've had to do ... for example ...


PS: There is another issue - not sure when it came about - but the Mac Mini doesn't always connect my BT Mac Wireless keyboard and mouse. When this fails - login fails too even when I use a USB keyboard/mouse combo (I have to reset my password via my Mac account - THIS IS THE STRANGEST thing ever). I'm thinking I have a few BT devices competing to be paired with the Mac OR more likely, I need to re-install Big Sur). BUT when the BT keyboard works ... so does login ... this one is such a puzzle for me just now ...

Jul 4, 2021 12:16 PM in response to pebear

I know you tried something like this but at least see if you can get it to work more straightforward or not. When you boot the M1 Mac Mini have both monitors connected. Go to Settings > Display and immediately make sure you aren't mirroring displays--have that box clear, not checked in the Arrangement tab.


Then set both monitors to default resolutions. For a Mac these may only be how the GUI displays text and icons--I go back and forth with Mac support and they aren't sure that streaming content and games are or aren't being displayed in their proper resolution even as the icons and text and browser / app panes gets bigger and smaller.


Then after both are set to default you try to use the alt if you want a higher manual resolution set:


Open System Preferences from the  Apple menu in Mac OS X

  1. Click on “Display”
  2. Under the ‘Display’ tab, hold down the OPTION / ALT key while you press on the ‘Scaled’ button alongside Resolution to reveal all available screen resolution options for the display
  3. Choose the resolution desired from the complete list of available screen resolutions; also
  4. Click Show Low Resolution Modes to display the refresh rates and maximum refresh rate you can get
  5. Exit


For any monitor for which you have succeeded in setting a higher resolution you could try to double check that you actually see a difference in resolution quality in full screen from the defaults from when you manually set higher resolution--yes from default to higher resolution the windows and the text and the GUI shrink--but when you go to full screen for the movie or game do you see a difference? For a Mac for working with text only or using text-oriented apps the default is probably a good bet.

Dec 6, 2020 9:41 AM in response to lukethesky

Thanks for pointing that out. I just checked my display information and as you said it seems like I my new monitor's refresh rate is working @ 30Hz instead of @ 60 Hz (Please see the attached screen shot). To be honest, I am not familiar with these hardwares so I didn't know what to do to solve this and the reason why I am trying to get a USB C to Displayport cable is because I found this Youtube video reporting a similar issues: https://www.youtube.com/watch?v=ZbJXETn0PuY


This guy had the exact same monitor and issue and went around the it with replacing HDMI with Displayport cable. It seems many more experienced the same issue and solved it with the same approach, as shown in the comment section.


I checked the j5create cable, but it says it's 4K compatible with 60 Hz refresh rate.


Dec 7, 2020 5:23 AM in response to Malcolm J. Rayfield

I've just received this exact cable and it does not work!


I am using 2 x Apple DisplayPort 27 inch Cinema Displays. One is plugged in with a DP to USB C adapter and working fine. Just tired adding another display using that connector and it does not work. Here is the output of the system profiler.


I wish you could use multiple DP adapter via USB c like in the Intel Mac Mini.


I will probably try the DisplayLink adapters next

Dec 8, 2020 5:02 PM in response to whatisdeadmayneverdie

Long time apple user, first time forum commenter.


I wanted to provide my experience of my M1 Mac Mini. Short version is that Apple support told me that a USB-C to HDMI or DP adaptor is not going to work (which includes the A2119 adapter that they sell - For reference if you only are using one screen it's fine, but it will NOT play nice with multiple displays) and that you MUST use something that's thunderbolt supported.


I ended up buying the Belkin Thunderbolt 3 Dock (F4U095AU) your milage may vary in different parts of the world given I think this was sold in AU. Using a Display port to Display Port cable that I got off Amazon I now have 2 screens at the same resolution and refresh rate. For anyone interested, this is my setup:



There is one catch, where no matter which screen i have setup for "primary" the displays always seem to reset to my "secondary" display always being on the wrong side (it thinks I have to mouse right instead of left) but aside from that small inconvenience, I have no flickering, and no other issues. But the engineering guys were very specific in saying that running 2 monitors using a USB-C adaptor and HDMI won't work at all.


Hopefully this information helps someone out so that they aren't tearing their hair out like I was!

Dec 9, 2020 3:59 AM in response to whatisdeadmayneverdie

Hi. I have issue but mine was a bit worst. It was generating application crash and I needed to turn it on and off again. My setup is 2x PD3220U and for it to work I need to use apple dongle to connect both via HDMI. Even tough the monitor has thunderbolt it is only displaying 30hz so BENQ advises you to use a dongle (until they fix this). For me it was crashing no matter what type of connections I was using. It was generating a crash report every time I connected 2 monitors. I spent hours and hours with Apple on the support, my case still not resolved. I was afraid that the problem was hardware, but it is clear software. I tried to reinstall the macOS but it didn't work (it does not erase everything), the only thing that worked is to full erase the Mac and than install with an external usb drive. There must be something on the shipped os that was preventing it to work. I am working for hours now and no problem. When you enter the boot option (holding the power button there is "hidden" option on the top left called "erase this Mac". That is what I did, and then I installed it back using a usb drive. It is working so far. let's see how it performs. And I am using HDMI - HDMI and than USBC - APPLE DONGLE - HDMI:



I will wait apple to come back with the analysis of my logs and I will share here. It is frustrating!

Dec 19, 2020 3:13 PM in response to Tokensalad

Going a little crazy here. Have done firmware updates on both monitors, waiting for next apple 2nd tier call on Monday. Meanwhile, I re-read the M1 Mini Spec sheet...


That very first line under Video Support says "simultaneously supports up to two displays"... it seems to imply one display MUST be a Thunderbolt Display and the other MUST be an HDMI (my emphasis).


Under "Thunderbolt 3 digital video output supports," it mentions adapter support BUT NOT simultaneous dual displays. Notice that?

Under "HDMI 2.0 display video output" it says support for ONE display. Does that mean, if you use the HDMI, you can only have one monitor plugged in?


I know reading comprehension is a thing, so I'm trying my best here, but maybe the thing is if we want dual monitor support we MUST be using one HDMI and one thunderbolt monitor? In other words, anytime you plug something into the HDMI port, the other monitor BETTER be a thunderbolt monitor, or it just won't work. So, even two thunderbolt monitors won't work, because you'll need a HDMI to thunderbolt adapter, which would then cause it to not work under the 3rd rule?


SOOOOO.. Is anyone running dual monitors using thunderbolt and HDMI, sticking to the first rule and getting it to work correctly?

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.

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.


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.

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.



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

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