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

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.

Hi, guys. I'm having the same issues. This looks like a Big Sur bug because I can fix it by changing the scale. Every time I turn on the computer, or it comes back from sleep, I have to change the scale and also the arrangement. Here is my post:

https://discussions.apple.com/thread/252071060

I'm going to wait a few days to see if any solution comes from Apple and then try with another adapter for the monitor connected to the Thunderbolt port. Currently, I'm using a USB C to HDMI adapter, so both monitors are connected with an HDMI cable.

Hahaha. Apple advisor had me purchase this adapter from their site and see if it works. I’ll know when it arrives tomorrow.

https://www.apple.com/shop/product/MUF82/usb-c-digital-av-multiport-adapter?fnode=8a0504c8bbb04c4ada6705eb02728099c7dc2b3b4e1e46282ecf7fe92ed2693c845d237f768939b3e6d14e919aa706674c4815681d4557d95e0eccdf6c34690de3f1a23bc3a1d02ab621e1fcaf5e7d7c8fb343b7da93472d478e5061971bfdf9

Do you need a developer account on apple to be able to download the beta version of Big Sur 11.1? My version is 11.0.1 and I went on https://developer.apple.com/download/ but there are no beta version showing there.

MacSupernova wrote:

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!

…

Then you’ll need to provide Feedback directly to Apple, such as through Product Feedback - Apple.

No amount of posting here will change any of that (except to the point that people’s suggestions, here, can help).

Hi there,

as many of you, I am also experiencing the same flickering issue with my Mac mini M1 (8GB unified memory, 512GB SSD).

I am using two identical ViewSonic VX3276-QHD (2k) Displays at native 1440p resolution.

I am in search for a solution since 3 days now. I tried some of the things proposed here as well (e.g. swapping the HDMI cables after booting just with the USB-C cable plugged in as described by chgough54 on page 3).

Let me share with you what else I have tried, so you might save some time and money in trying to find a solution.

All of the following didn't solve the problem for me:

• Updating to macOS Big Sur 11.0.1
• Updating all installed Apps to the latest version
• Disabling all Login Items
• using HDMI -> Displayport cable
• using HDMI -> HDMI cable
• using USB-C -> Displayport cable
• using USB-C -> Displayport cable
• Booting in safe mode
• Booting in diagnostics mode
  • diagnostics test always get’s interrupted with an error message after checking the network connections (no matter if ethernet is connected or not) that tells me to start it again by using diagnostics boot
• Using the guest user account
• Creating a new user account
• SMC reset
• NVRAM reset
  • holding ⌥+⌘+P+R on boot for at least 20 seconds didn’t do anything noticeably for me, not sure if it worked or not, couldn’t perceive anything, tried it several times
• Reinstall macOS Big Sur

I had a chat session with the Apple support yesterday for almost 1,5 hours with the result that they recommended me to reinstall macOS Big Sur. I tried it today, but had no luck as you can see in the list above.

Following that, I called the Apple support and reported, that the reinstallation didn’t help and that I’m out of ideas. The only other thing that they could come up with was to completely erase / format my hard drive and perform a clean and new  installation of macOS Big Sur.

I am actually a bit reluctant to do this and gladly I came across this support thread here which gave me some relief as I now see, that I am not alone with this problem. That also made me think that probably a complete erase of my hard drive won’t fix that issue either, as it might be a Big Sur software or hardware issue when so many people experience the same thing.

But let’s keep hoping and searching for a possible solution.

Maybe Apple finds this thread and looks into these issues soon.

Lars

I have an update to my situation. Now the problem is solved with my new (temporary) settings.

Original settings:

• 2 external monitors (LG: 24MK430H-B & 22MK430H-B) (Same model, 24in & 22in)
  • https://www.lg.com/ca_en/desktop-monitors/lg-24MK430H-B-led-monitor
• Mac Mini>USBC-to-HDMI adapter(Belkin)>HDMI cable>LG:24in & Mac Mini>HDMI cable>LG:22in

///// Change: I replaced my LG:24in monitor with a new monitor (LG: 27UD68-W) and replaced USBC-to-HDMI adapter & HDMI cable I was using for this monitor with a new USBC-to-HDMI cable.

Current settings:

• 2 external monitors (LG: 27UD68-W & 22MK430H-B)
  • new monitor: https://www.lg.com/us/monitors/lg-27UD68-W-4k-uhd-led-monitor
• Mac Mini>USBC-to-HDMI cable(j5create)>LG:27in & Mac Mini>HDMI cable>LG:22in
  • new cable: https://en.j5create.com/products/jcc153g

Since I changed my settings I've restarted my computer more than several times but I'm not experiencing the issues even once. I am now ordering another cable (QGeeM: USBC-to-Displayport cable)(https://www.amazon.ca/gp/product/B074V5MMCH/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1) to replace my USBC-to-HDMI cable(j5create) due to an unrelated laggy mouse issue, so once I receive and replace it I will post another update explaining whether it's working or not.

I wrote my setting that worked earlier today, and I received a new cable just now and tested it and it works too.

Here are the two settings that are working perfectly without any issues so far for me:

[Setting 1]

• 2 external monitors (LG: 27UD68-W & 22MK430H-B)
• Mac Mini>USBC-to-HDMI cable>LG:27in & Mac Mini>HDMI cable>LG:22in
  • USBC-to-HDMI cable(j5create): https://en.j5create.com/products/jcc153g
  • HDMI cable (random one I've been using for long time)

[Setting 2]

• 2 external monitors (LG: 27UD68-W & 22MK430H-B)
• Mac Mini>USBC-to-Displayport cable>LG:27in & Mac Mini>HDMI cable>LG:22in
  • USBC-to-Displayport cable(QGeeM): https://www.amazon.ca/gp/product/B074V5MMCH/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1
  • HDMI cable (random one I've been using for long time)

I've always had issues when using adapters (USB C to HDMI) but since I started using cables that directly connect Mac Mini and the monitors the issues seem to have gone away. I am not here to suggest direct cables are the answers, but I hope my report helps anyone find a solution to their issues.

Just adding my 2 cents and experiences here (have the EXACT same problem as everyone)...

1. Have M1 Mac Mini (16GB/512GB FWIW, but don't think it matters). Mac OS 11.0.1.
2. Have two Lenovo Q27 QHD screens, identical - they have HDMI + DP inputs.
3. Used high-quality HDMI 1.4 and HDMI 2.0 cables, HDMI to HDMI.
4. Used TB3 to HDMI (ver unknown, assuming <= 1.4), TB3 to DP, single cables, adapters, dongles, etc.
5. Not listing out all the various adapters but they are reasonably high-quality; none are Apple-branded.
6. All of these cables, dongles, adapters, etc. work perfectly in a Windows 10 multi-monitor environment.

Problem = upon screen wake (and I even have the "don't sleep when screens are off" checked in the Energy panel), one and/or both screen(s) will flicker, be unresponsive, stay black with no background, etc. This happens when Big Sur sets the monitors to different refresh rates. Sometimes the BT mouse will work well so I can just launch Displays, change the offending monitor's refresh back to 60Hz, and re-arrange, but sometimes not. The other solution is to manually turn off the "black" screen, turn it back on, which triggers something that fixes the issue (still need to re-arrange, but at least Big Sur recognizes the screen).

My conclusion = definitely a software bug/issue. Apple needs to fix this and I presume they will given all the noise/experiences/feedback from the user community.

My work-around solutions = launch Display panel if you can, gather windows, set refreshes back to same Hz, re-arrange. If that doesn't work, turning off the offending monitor and turning it back on has the same effect as plugging/unplugging the monitor's cable and forces Big Sur to re-recognize the screen. Then open Display panel and re-arrange.

This is annoying but at least I can work on 2x screens for now. I turn off sleep which consumes more power of course, but that's a relatively small price to pay vs. just using one screen, and I hope Apple fixes this soon.

I have been following this issue in several threads across Reddit and the web and am still having consistent issues. I have brand new dual 4k 28" monitors (BENQ EL2870U) and have tried everything I've seen suggested to fix the problems without success.

DUAL MONITOR ISSUES I'VE BEEN EXPERIENCING

1. One monitor will flicker lightly (usually the thunderbolt to DisplayPort)
2. The display arrangement in Mac OS will get reset constantly. The system can’t remember the order of the two displays. This happens all the time on restart, or if the Mac mini wakes from sleep. It will also stop showing me the arrangement tab in the display preferences sometimes so I can only select the “Display” or “Color” tabs after this happens.
3. Sometimes the BENQ EL2870U display profiles under the “color” tab in preferences are not present and it only shows a custom profile called “SD 170M-A” or a similar HD version.
4. Both monitors will show a black desktop and FLASH (not flicker) about every 3-5 seconds together. Sometimes I can go to the display preferences and change the settings or enable HDR and it stops (functions normally for a while)
5. Sometimes I will see very slight vertical pixel lines on one of the displays after using it for a while successfully.

I started on Mac OS 11 with Big Sur and was using the stock HDMI cable that came with the monitor along with a USB-C to HDMI cable to run the second display. However, I quickly realized that I needed to use an HDMI cable for one display, and a thunderbolt (USB-c) to display port on the other display for it to work properly, so I purchased 4 different cables to make sure it wasn’t a single brand of cable causing the problems.

I have settled on the following two cables and am currently using these..

1. https://www.amazon.com/gp/product/B07RZ8V78S/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1
2. https://www.amazon.com/gp/product/B07CL31FR6/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

I upgraded to Mac OS 11.1 and it was still happening so I moved to Mac OS 11.2 (beta) and it’s STILL HAPPENING. I would argue it’s actually worse on 11.2 after upgrading and now I’m considering rolling back to 11.1 but I don’t have much confidence that it will fix the issue because it didn’t work prior to the upgrade.

BTW it’s an M1 Mac Mini with 8GM RAM and 512GB HD. Both displays are in 4k @ 60 so they should work from everything I have read. I am considering returning it and trying the 16GB machine to see if it might help solve the issue, but that seems counterintuitive.

Has anyone actually solved this permanently? Anything I have missed here that you would try? It’s incredibly frustrating (to say the least). Not sure if I’ll just need to wait it out, or if I might have a hardware issue, etc.

Any help, tips, etc. is greatly appreciated.

Here is a video I just took of the issue after posting this. https://imgur.com/gallery/p7PVD47

I have the 16GB/512SSD. Exact same problems as you. Here's my plan:

I've got a "senior tech" person calling me back tomorrow from apple (after two days of trouble shooting and screen sharing). Depending on how that call goes, I'll either:

1. wait for a software update and live with it until then
2. order a new one (and get the 1TB HD) and cross my fingers.

I'll post here and let you guys know what the apple tech tells me.

Spoke to the apple tech again today. She is stumped. She's a level 2 tech and she's trying to communicate with an apple engineer (who's not replying for two days) to get the next steps and is trying to replay that info to me. We're trying to use sysdiagnose and snoop timer, but she doesn't know the steps and we have to wait for an apple engineer to get that information to her so she can relay it to me. Fun.

In the meanwhile, I've gone ahead and reordered a new Mac M1 Mini.

Here are the steps we've tried so far and the steps we're stuck on. (note of warning: do not try to create a USB boot disk to wipe the internal SSD unless you have a second Mac to recover it with using Apple Configurator 2. I did and went down a 3 hour rabbit hole last night. Long story short: it matters which USB port you plug the mini to the other Mac with). Anyway.. here you go:

Steps tried:

• Unplug all cables on displays for 1 min
• Used a variety of HDMI cables
• Factory reset displays to default settings.
• Deleted the following files (from BOTH /Library AND ~/Library:

/Library/Preferences/com.apple.windowserver.displays.plist

/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist (where * is a random text string)

• Do not use “auto” select on the monitor. Set it to the actual display connection type.
• Full wipe on internal SSD via USB boot disk, secondary Mac and apple configurator 2. (I did this on my own outside of apple’s advice.)
• Update firmware on monitors
• Factory rest both monitors
• (Stuck here. not tried.) Capture data with sysdiagnose
• (Stuck here. not tried.) Timing snoop

Display problem persists. Mac mini M1, 16GB/512SSD. Big Sur 11.1 (20C69)

It's a perfect storm of several things that nobody really appreciates, plus a couple of things that are obvious when you think about them. The obvious things are that previous Apple chips have been used in devices that have a single display, and that, as a result the ability to drive two displays is less well tested at this point (versus the Mac Mini, which had either a standard discrete GPU or for the Intel models an integrated GPU that was already in use in the PC market, where multiple displays are quite common).

The things nobody appreciates have to do with HDMI, DisplayPort and Thunderbolt, namely:

• HDMI, DisplayPort, USB (even over USB-C) and Thunderbolt are all different protocols; they are not natively compatible as is sometimes supposed.
• While you can get passive adapters that let you connect HDMI to DVI, DisplayPort to HDMI, USB-C to HDMI and so on, this works because of special compatibility modes built into the various standards.
• Compatibility modes generally can't be chained. For instance, a passive DisplayPort to HDMI adapter plus a passive HDMI to DVI adapter won't necessarily work. Active adapters may make that work in some cases — or they may not — depending on whether they implement the required compatibility mode support.

For instance, USB supports DisplayPort Alternate Mode, Thunderbolt Alternate Mode and HDMI Alternate Mode. Thunderbolt can carry DisplayPort (as well as having a compatibility mode for DisplayPort-only devices), so it's possible to have DisplayPort over Thunderbolt over USB. Physical DisplayPort implementations are likewise often "dual mode", and can switch to using an HDMI or single-link DVI signal when they detect that that's what they're connected to. But Thunderbolt and the USB alternate modes don't support that. To add further confusion, some devices with DVI connectors can output HDMI signals but out of a DVI socket (yes, they really are different; HDMI is compatible with single-link DVI, but not other variants). And for extra fun, higher resolutions and refresh rates might require either dual-link DVI or HDMI, and obviously some devices may support both kinds of input.

So, why does this all seem to work for PC owners? Honestly, it doesn't always. Many PC owners have been saved largely by the fact that their graphics cards still sport DisplayPort or HDMI rather than Thunderbolt or USB-C connectors.

An additional complication with the M1 Mini is that it doesn't support HDMI Alternate Mode on its USB-C ports. That means that passive USB to HDMI adapters won't work.

Finally, the data rates required by modern displays mean that there are plenty of old cables out there that won't work or won't work reliably. Usually the cables that come with your display should be OK. Cable vendors are supposed to indicate compatibility with the various standards (and the various data rates) using a set of fairly confusing symbols, which don't necessarily make matters much easier either.

Anyway, hopefully that's all helpful to someone :-)