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

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!

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:

I spent about one and a half hours with Apple on the phone this weekend - they called me, rather than me reaching out to them. The good news is that the folks at Apple have seen this discussion and are aware of the problems. They did some diagnostic testing with me and downloaded all the required logs etc. It would appear they have a "multi-monitor team" working on these issues.

For now I've only had a success with USB-C to VGA cable. That's the only thing that's been stable and enabled me to use two monitors.

Let's hope they can make an update to solve all these issues...

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!

WEIRDNESS.

So, I had been using the VGA to USB-C Multiport adapter and having all these issues. I noticed that one of the problems was I was constantly having to rearrange my monitors because the Mini always wants the HDMI to be the secondary screen. I couldn't do that with my current setup because I was using VGA. So, I bought the USB-C to HDMI Multiport adapter and I arranged the monitors the way the Mini seems to want to have them, with the main monitor being on the left and the secondary on the right, everything sort of in the default position, and man, I can't reproduce ANY of my old problems! This seems to have fixed it for me (So far). It's only been around 4 hours since I started using the HDMI adapter, so we'll see how it goes, but so far, my problem seems to be gone. Solution? Updated to 11.1, using the HDMI out on the back as the SECONDARY display and the USB-C to HDMI Multiport adapter as the main. No idea why that works, but it seems to be working now. Here's a cautionary yay. yay.

Confirmed!!! The beta of Big Sur 11.2 beta 2 fixed all my issues. Now running dual 4K monitors without issue. The flickering has stopped and It’s keeping the arrangement on restart now as well. Woot woot!

So knock on wood but it looks like 11.2 might fix this issue I was seeing. Installed it and did a couple of tests putting the Mac Mini to sleep and waking it up. Both times I tried everything was the correct 2560x1440 60hz waking from sleep with the same dual displays, one HDMI -> HDMI (HP 27"), one USB-C -> DP via OWC Thunderbay 3 DP port (Eizo 27"). Fingers crossed it stays this way!

I don't know if this may be helpful to anyone, but I just bought and setup my mac mini m1 and I had the same issues with my j5 create Dual HDMI Mini Dock for some reason the displays were mirroring and I could not get it to detect it as separate displays. So I tried my old iHome adapter display and that worked for me. So my setup is the HDMI cord in the back of the mini and I have my iHome USB-C adapter plugged in the back as well with my HDMI plugged in the adapter.

Hope this helps!

Plug in the hdmi screen only and reboot then use the usb-c to usbc(display port n monitor) and plug it in…. If it does not spark into life then shutdown Mini… press and hold in power button until the maintenance boot starts , shutdown then restart , that fixed it for me, I have a 27 touch screen as hdmi to hdmi and a Samsung 49 extra wide screen for the usb-c to usb-c (display port set as connection on monitor)

Yes, johnthemacfan, not all USB-C cables are created equal.

With the M1 Macs, having USB4 ports (supporting the Thunderbolt 3 and DisplayPort options), the simplest bet is to go with (what Intel markets as) “Thunderbolt 4” cables: such cables are guaranteed to support all USB4 modes, in both directions.

(Admittedly, “Thunderbolt 4” cables may well be the most expensive you may find, out there, but it can help to not have to worry about what USB-C cables support what USB4 modes.)

I am MacUser since 1994 and only on the Amiga I had more flickering :-).

Here is my solution:

Only display port works. You need a USB-C to Display Port adapter. It plugs into the Thunderbolt port. Everything else didn't work for me.

Also, an Elgato Thunderbolt dock works.

https://help.corsair.com/hc/en-us/sections/360010576211-Corsair-Thunderbolt-3-Dock

Bye

TC

The M1 Mac Mini is an immature product. Apple should not have released it without making sure that it works with Big Sure 100%. It's probably 75% maybe 80%. My HDMI connection was not working because the other monitor had a much higher resolution. I had to boot both monitors on a Windows PC to figure out the maximum resolution on the HDMI monitor. Then I had to Mirror both monitors. Once I did that, I held down the ALT key / and bring up the resolution. I had to choose the HDMI monitor and chose the maximum resolution for the HDMI monitor then it came on and no longer out of range. Then I un-chose mirror and everything is up. I tried to set the other monitor at its max resolution but that only put the HDMI monitor out of reach again. So, they are both set for the same resolution. Then the Mac Mini went to sleep, and I had to turn off the sleep function in power settings to make sure that the monitors don't go to sleep. Going to sleep just reset the first monitor to his normal setting and put the HDMI monitor out of range again. So, I turned off the sleep function and set up the screen saver. So what works and does not. The HDMI does work. The multiple monitors do work. The power functions cause the monitors to forget their resolution settings (Something I have never seen in Windows happen). So, the power function does not work as advertised. Being able to set the resolution of both monitors to separate resolutions. This does not work on the M1 Mac Mini. Something I have never had problems within any version of windows since Windows XP. Apple needs to make hooking up varied monitors much easier. If Microsoft can do it so can Apple. If Linux can do it, so can Apple.

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.