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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

Top-ranking reply

editguyus

Level 1

4 points

Posted on Feb 19, 2021 12:30 PM

OK this is more of a specific response, mainly to anyone attempting to connect TWO Apple 30" (maybe other sizes too?) Cinema Displays to an M1 Mini. I am writing this all to document for anyone else in the hopes that they don't have to jump through all the hoops I did, also for my own reference later as the issue is not resolved!

Bought a new M1 mini (16Gb of RAM) in January; after reading SOME threads and watching a couple YT videos (like the one where the dude hooks up 6 monitors), I was confident that it would take some trials but all I had to do was figure out the right set of adapters and I'd be golden.

My monitors are the older ones, not Thunderbolt, so already were running to my 2013 Mac Pro via the expensive dual-link minidisplayport to DVI adapters. I tried this HDMI cable before my mini even came, no dice so I sent it back.

Then came the onslaught of attempted cables, some using the minidisplayport adapter and others including the Startech USB adapters that have their own GPU card.

Didn't work: this this this this and this

These 2 USB-C/Minidisplayport adapters DO work, at least in connecting ONE of the monitors:

https://www.amazon.com/gp/product/B01N4FQNYW/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B08B7FSVTL/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Finally discovered Apple had an HDMI-DVI adapter, so had to try that, right? No dice, sent it back.

Then I moved to the DisplayLink software route, trying this Startech adapter as well as a single display adapter(using another adapter in the middle, which seemed to work but then would fritz out. Then it really just wouldn't work.

Oh also forget trying to sleep the computer and then hoping the displays would wake up too, I would always have to re-plug in the cords to get anything to show up. I spent time in Safe Mode, Recovery mode, tried changing the desktops (now there's this new adaptive desktop that changes sunlight throughout the day, could that be it?--eventually figured out, no that's not the issue). Note that this is pressing option while changing the resolution in Displays system prefs to toggle different things here and there, trying all kinds of combinations and forgetting which ones I'd tried and then trying them all again. Oof.

Then I read that 11.2 fixed the displays problem! Oh, the problem was actually in the OS?! I guess I had given Apple too much credit and assumed it was the adapters. So I pre-emptively rebought that Apple HDMI-DVI adapter, giddily updated, and upon hooking it up--it... didn't work.... but now I COULD get the HDMI-connected display to come on in lower-res mode, at least on startup.

I kept reading more and more, but could not get the 2 displays to come online at once, ever, for more than 5 minutes. So I finally scrapped the notion of even trying for 2, but then read this article about resetting the color calibration, so I tried it.

I had already tried creating new calibrations settings (I thought), but wth ok, I gave it a shot: and lo and behold, the 2nd display (connected via HDMI) would come on! ...so long as I left it in 1280x800. Tried a lot of other things to no avail, and FINALLY called Apple.

Got escalated, and spoke with a tech who spent some time looking through Engineering notes. Came up with the pronouncement that 2 Cinema Displays will NOT work with the M1 mini, at all. !! Wait what? I told him that I was seeing the second monitor, so long as it was in 1280x800 (or less), and it did appear stable. He said that according to Engineering the company is surprised by that. We ran through a number of alternatives most of which I had tried, but apparently the company believes I should not be seeing ANYTHING on the 2nd monitor. Welp. OK, he wrote it down, said they may call me back, and here I am, still enjoying these monitors and hoping for an 11.3 fix (not holding my breath).

So, to recap, I am using one display connected via USB-c to minidisplayport to minidisplayport-DVI adapter, and the other is Apple's HDMI-DVI adapter right to the DVI connection (with all USB 2 cables plugged in too). I sent back the DisplayLink gear after the tech I spoke with said that it was a dead-end, that anything with an external GPU was uncharted or dangerous waters in terms of the M1 chip. And I have 1 and a half working displays. (OH btw I DID try using a different monitor via an HDMI cable, it worked fine 1920x1080 so at this point I think the dual-display issue (so long as it's not 2 ACDs) is solved in the 11.2 update, at least as far as I can see with a basic TV monitor via HDMI along with the aforementioned USB-C connection to my ACD)

I'm sure I forget a whole set of attempts to fix this, but I hope this helps someone. Or Apple to fix whatever the bug is. Til then I'll limp along with my half monitor and consider buying a new one (but I LOVE these old LCD monitors! so little glare!). Good luck.

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380 replies

mattd313

Level 1

33 points

May 14, 2021 7:51 PM in response to SGD-Tralee

I’m familiar with using dual monitors; I’ve used two on my Mac Mini 2012 for almost a decade.

The issue is I have several things on my secondary monitor, and sometimes when I leave my desk and come back later, all windows I left open have been moved to the primary monitor.

May 24, 2021 4:28 PM in response to whatisdeadmayneverdie

I bought a Lenovo portable monitor to be a second screen. I connected it via a USB C 3.1 cable to the USB C displayport interface on the monitor -- it doesn't have an HDMI input. It would work sometimes, then especially after sleep, it wouldn't come on. I had to unplug and replug, which worked most of the time, but not always. Then I bought a USB C cable rated for 20 Gbs, i.e., a USB 3.2 cable. It worked immediately and hasn't has a problem so far even after displays go to sleep. It comes right back up, no more plugging in and out. I'll come back and edit if the problem re-appears.

Halliday

Level 4

2,677 points

May 24, 2021 4:55 PM in response to johnthemacfan

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.)

Jun 11, 2021 10:07 PM in response to whatisdeadmayneverdie

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

Jun 13, 2021 2:00 AM in response to MacSupernova

I'm afraid I have to revise that. The flickering is back again. I have now tested on the DVI to HDMI. That works, but then only with 30 Hz. Apple needs to fix the firmware. Thanks Apple!

Acer CB281HK:

Auflösung: 3840 x 2160 (2160p/4K UHD 1 - Ultra High Definition)

UI sieht aus wie: 1920 x 1080 @ 30.00Hz

pebear

Level 1

4 points

Jul 4, 2021 10:00 AM in response to whatisdeadmayneverdie

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.