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

Top-ranking reply

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

kimac

Level 1

25 points

Dec 2, 2020 2:01 PM in response to lukethesky

lukethesky, what brand adapter were they? the one I posted above says it supports m1

sputnixk

Level 1

4 points

Dec 6, 2020 8:00 PM in response to taro0922

I'm not sure the spec of HDMI cable I am using to be honest. I bought it from random shop few years ago.

Monitors are two identical HP Z27n monitor with resolution of 2560x1440.

Dec 7, 2020 7:11 AM in response to Elarson6772

Now I tried a USB-C to Mini-DP Adapter (connected to a Mini-DP to DP cable) and nothing has changed. So don’t waste your money on that.

rpfleger

Level 1

4 points

Jan 14, 2021 4:53 PM in response to PetecoEdit

Downloading macOS Big Sur 11.2 Beta 2 with high hopes that it resolves the M1 dual display issues. Will report back ASAP!

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

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.

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...

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.

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?

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.

Nov 24, 2020 10:31 PM in response to Tnt7982

Well I'm just happy you were able to find a solution for your setup. Enjoy the dual screen system with the M1. I don't know about you but aside from this issue, I'm loving this little yet powerful machine.

Have a great Thanksgiving week!

Nov 24, 2020 10:37 PM in response to rdf7777

A Mini Display Port display won't work from a computer's HDMI port with a simple Mini DisplayPort to HDM I adapter. Those adapters are for connecting HDMI displays to computer Mini DisplayPort, and won't work in the opposite direction.

To connect a Mini DisplayPort display to a computer HDMI port you need a HDMI ti Mini DisplayPort converter.

https://www.newegg.com/p/183-00BG-00004

Note that even with the correct connections, there are many reports of displays not working with M1 Macs.

rdf7777

Level 1

8 points

Nov 25, 2020 2:19 AM in response to Malcolm J. Rayfield

Thanks that is the exact adapter I bought (from Amazon) and nothing. Are you all rebooting your machines with both monitors plugged in? The USB-C to MiniDisplay port works fine. Just the HDMI. Ordered another set of three adapters to try and piece together later today.

Nov 26, 2020 1:45 PM in response to whatisdeadmayneverdie

I have the same problem in my new Mac mini M1 with dual monitors.

Additionally, my monitor connected to HDMI directly doesn't have resolution rate 3008x1692 (which is the best in my 28' monitor, 4K has too small images). Does anyone has this problem in the monitor connected to the Mac mini HDMI port?

kimac

Level 1

25 points

Nov 26, 2020 5:42 PM in response to BillyBrown301

that's good to hear because some people said the vga fixed the issue..it must be a Big Sur and M1 problem with HDMI...my main monitor plugged into the HDMI out works fine...only when I introduce a second one does it give me problems

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