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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

ffh111

Level 1

11 points

Dec 18, 2020 7:53 PM in response to whatisdeadmayneverdie

This is crazy, as I thought it was just me.

Mac mini 16/512

Dell 4k (S2721Q)

Lenovo 2k L24q-30

Both are 2020 model monitors.

Here is the scenario.

If I use a (usb-c > DisplayPort) cable to feed the 4k dell on it's own, everything will work fine. The second I plug in a HDMI > HDMI cable to the Lenovo, as a dual monitor, the dell starts turning off and on every few seconds.

I've tried using a different (usb-c > DisplayPort) cable and the issue still persists. The only solution is to use the (USB-c > displayport) cable on the Lenovo and use HDMI to HDMI on the 4K Dell.

But here is the kicker, while it seems to work fine, the second it goes into a deep sleep, the mini forgets the custom settings of the displays.

Also, if I plug these same monitors into my Win 10 powered dell 8930 via the NVIDIA 1050ti card, the issue disappears.

Dec 19, 2020 12:38 AM in response to pmiles

Pmiles, I'm really not a pioneer, I'm a paying customer. As a developer, I am not completely unsympathetic to teething issues on release. However if I release a product, and there are problems, I immediately: own those problems, explore them, give estimates on when they will be fixed, and fix them. It's great that Apple has created this truly amazing advance in chips. Nevertheless, forgetting to get the basics right: attaching a screen, operation through mouse and keyboard (bluetooth issues), is pretty unacceptable. I am happy to beta test for Apple, but in that case they should take a deposit rather than the full amount and make sure I am aware that the product is not ready.

bt017

Level 1

5 points

Dec 19, 2020 11:27 AM in response to Tokensalad

Talked to the apple tech this morning... they had me do this: (It still didn't work tho).

Apple Support:

1. Unplug all cables on displays for 1 min

2. Factory reset displays to default settings.

3. Deleted the following files (from BOTH /Library AND ~/Library:

a. /Library/Preferences/com.apple.windowserver.displays.plistBehost/

b. /Library/Preferences/ByHost/com.apple.windowserver.displays.XXXX.plist

4. DO not use “auto” select on the monitor. Set it to the actual display connection type.

5. Update firmware on monitors

I'm stuck right now on updating the firmware on my monitors. I don't know how to do that, so I'm researching that right now, then I need to leave apple a voicemail and I'll continue with the tech from there. Still working on it. Still not working.

Dec 19, 2020 11:52 AM in response to bt017

Thanks for this. You have actually resolved another bug that I encountered. My screen was stuck in 270 degree rotation (I tried it but changed my mind) and would revert back to it whenever I restarted. since this is also the only monitor that would come on at startup, it meant I had to type my password at an angle. Deleting the file in step 3a, has resolved that.

Cheers

Dec 19, 2020 4:23 PM in response to bt017

Hi bt017, I can confirm I am running two monitors at the same time; one through hdmi port and the other through usb-c. When I first got the unit I was getting the flickering but after updating to 11.1, no more issues and both displays work flawlessly.

I have removed my unit from beta program to stay on 11.1. On one of my previous post you can see the adapter I’m using.

once again, I can confirm that two displays work simultaneously.

rgaeti

Level 1

4 points

Dec 20, 2020 6:29 PM in response to whatisdeadmayneverdie

Hi, I have the Mac mini M1 16GB and 2TB SSD. I had an even worst problem with mine. When it arrived I plugged the 2 monitors ( BENQ PD3220U) and it worked for a while (one in USBC and the other on HDMI) after a few hours, started flickering and crashed. After the crash I was not able to plug both monitors because it would cause a kernel panic. I raised a ticket to apple (no solution). I decided to wipe my Mac entirely (not reinstalling - I did before and did not work) and install with a second HD. It worked. The problem is that every time I turned off the arrangements the settings were gone. I upgraded to Big Sur 11.1 and I got it completely fixed. No flickering, no crashes and the arrangements are kept. The trick situation for me is that the PD3220U has an issue with the M1 the only way to run it both with 60Hz is to use the apple dongle and convert USBC to HDMI. Based on what happened to me it seems that when the monitors are at different Hz the system goes crazy. But with the USBC-HDMI dongle I am now able to work with dual monitors.

I would like to run both monitors at 3008x1692 but only the one connected to the USBC port has this option, so now I am running both at 2560x1440. Not optimal but ok.

As there is no way to reset the NVRAM, PRAM and SMC I needed to clean install (erasing it completely before installing the OS using an external USB drive). It worked for me and I hope it helps you out.

Dec 21, 2020 5:33 PM in response to whatisdeadmayneverdie

This has been a pretty frustrating thing for me too. I have an M1 Mini (16GB RAM/2TB SSD) running two BenQ PD2700U monitors. The right monitor is a direct HDMI connection to the Mini. The left monitor is attached via DisplayPort cable to a CalDigit TS3 Plus hub (which is in turn connected to the Mini via Thunderbolt 3). Prior to the 11.1 update, both monitors would flicker, resize, go black, and all sorts of assorted weirdness anytime the machine went to sleep. The only way to correct it involved unplugged the HDMI cable from the Mini and plugging it back in. After the update, the problem seemed to vanish, but has now changed to the monitors both occasionally resizing to a different resolution when I wake them. Turning the right monitor on and off again corrects the problem immediately. It doesn't happen every single time the monitors wake from sleep, but it is'a good percentage of the time. At least I don't have to physically unplug anything now.

Dec 22, 2020 1:45 AM in response to Joshua Mitchell

Yours is, more or less, what happens to me when using two identical ASUS monitors. But I have now found out something that further confuses me. I have an HP usb-c portable monitor. Just for japes, I plugged it in along side the monitor that is connected directly via HDMI, the same monitor that generally restarts at a 270 degree rotation. What is really weird is that now, both screens behave as you would expect. The HDMI monitor always starts in the proper rotation, even from sleep. So it looks like something about the Thunderbolt port controllers is impacting the HDMI port.

Dec 27, 2020 10:33 AM in response to whatisdeadmayneverdie

Same problem with MacMini M1 2 TB/ 16 GB. Plugged in my two old Samsung Full-HD monitors using HDMI (1) and a USB-C to HDMI cable (2). Black and white flickering. Tried several USB-C Dongles as well as my CallDigit Thunderbolt Dock using different cables. Doesn´t work. Hope Apple takes this serious. I need this machine for work with two screens until my new monitor arrives ...

bt017

Level 1

5 points

Dec 28, 2020 4:14 PM in response to whatisdeadmayneverdie

Apple tech just called me back this morning (12/28/20). She had no more steps for me to try. Said apple engineers are aware of the problem and are researching it. She said she'd call me back with either steps to try or an update to get. She didn't give a time frame.

Sounds like apple's working on it then.

msct-m1

Level 1

4 points

Dec 29, 2020 6:35 AM in response to bt017

Just an FYI, agreed/confirmed there are all sorts of M1 Mac Mini issues with dual-display (16 pages on this thread alone!) It should "just work" but it doesn't, for whatever reason - but there's enough of a hub-bub that Apple seems to know about it and is working on it... I happen to have two (2) identical Lenovo Q27 screens (QHD native resolution, HDMI and DP) and have refresh/flickering/reset issues after sleep as well.

The 11.1 update helped things greatly, but I can report that we've taken a step back with the 11.2 beta for whatever reason. There are work-arounds that I have figured out (turn on one display, log in if Bluetooth isn't affected from wake - sometimes it is and the Magic Keyboard doesn't work properly - then turn on the other display). Bottom line = I need to remember to physically power off both displays before leaving and going to sleep, and then turn them on one by one after the Mini is awake... akin to unplugging and plugging back the connection cable. Having both displays on power-save (amber light) and then waking the M1 Mac Mini, thus waking both monitors at the exact same time = highly problematic and unpredictable. After trying every cable and adapter known to man, I am 99.9% confident it's not a cabling issue and simply some bug or problem with the way the M1 Mac handles dual displays as my HDMI and DP are both "native".

My current solution still requires going into Display control panel to re-arrange each time when each monitor turns back on and reverts to native resolution and common refresh (60 Hz), but I can live with that right now... ah, the price of early adoption, but it's worth it in my opinion!

Dec 29, 2020 3:25 PM in response to whatisdeadmayneverdie

I followed all 16 pages of this thread in the hope that it would help me connect a 3rd monitor to my new 16 GB M1 Mac Mini, and was surprised to see that so many had trouble getting two monitors to work. I have not had any problem using two monitors. I guess that I am lucky, as I am certainly not an expert in computers. FWIW, here is my set up:

The left side monitor is a Dell model 2007 FPb monitor (1600 x 1200 @ 60 HS) connected via Thunderbolt on the Mac Mini to DVI on the monitor.

The front/main monitor is actually a Westinghouse TV model LD2240 (1920 x 1080 @ 60 Hz) connected via the Mac Mini’s HDMI to HDMI on the TV.

Because the computer is being set up exclusively as a Flight Simulator, I would like to be able to look out on both sides and through the front windscreen. I do not need gaming quality graphics, so the current monitors do the job, and I am getting frame rates in the mid 30’s. Before any gamers gag at that FPS, it is in the sweet zone for X-Plane. What it will be with 3 monitors remain to be seen.

bt017

Level 1

5 points

Dec 29, 2020 4:15 PM in response to whatisdeadmayneverdie

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.

Dec 29, 2020 4:39 PM in response to 1HungLo

It is running very well with two monitors. I am getting FPS in the mid 30’s with the resident C-172 at KSEA and settings as follows:

# World objects: Max. Reflection: Min. Parked Aircraft: On. Shadows on scenery: Not On. Metal: On. Visual effects: Max. Texture: High. antialiasing: FXAA. Anisotropic: 2X. Using Logitech Saitek Yoke, Power Quadrant, Rudder Pedals.

Apologies for the off-topic post, but the question was asked.

bt017

Level 1

5 points

Dec 30, 2020 8:32 PM in response to whatisdeadmayneverdie

It's been a little over 24 hours and I just saw one tiny glitch. I saw TV snow on my secondary monitor for a second, then it fixed itself before I could do anything. Seems like the problem has 99.9% gone away with the new adapter. Very weird.

Thing is, I already ordered the replacement mini. I've currently got the 500SSD and the replacement will have the 1TB SSD. So, I'm still replacing this one, albeit on my dime.

Anyways, things are looking good.

Good luck!

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