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

Big Sur 11.1 is available for all. And I can confirm it solve the issue. Thanks Apple engineers.

Yeah, me too. I installed the update of Big Sur 11.1 last night and I can confirm that the screen flickering on my dual display has stopped since the update.

Mac Mini hdmi port ->hdmi in on monitor 1

Mac Mini usb-c -> usb-c in on Monitor (display port in)

no adaptors , just native cables

using 11.2 update

problem has been solved with Big Sur update, it wasn't the cables at all.

I have the same problem. talked to apple senior support. tried a fresh reinstall of Big Sur on my Mac mini M1..no help...must be a software issue...affects all three monitors...one is connected via hdmi, the other usb to hdmi adapter, the third using display link usb 3 to cdmi (yes I've tried with and without that adapter connected...)

hopefully an update to Big Sur will fix it...

the only way I know how to fix it is to change the refresh rate on the monitor (inside system pref) from 60 to 50 then back to 60...

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.

It looks like this one is working for me (for now, anyway). No fiddling around required after sleep or a reboot.

VAVA USB C Hub, 9-in-1

https://www.amazon.com/gp/product/B079GSMZ7G/

Also, none of the other things worked for me, VGA, changing refresh rate, etc.

is there a beta 11.0.2? I talked to senior support today again and we closed my case with no solution...I tried the apple certified M1 usb-c to HDMI adapter and it did not fix the problem.

It's def a Big Sur issue with M1 Macs, multiple (not single) external displays..

and it's fixed upon changing refreshing rate from 60 to 50 then 60 again, at least on my machine...my monitors are Hewlett Packard, HP24mh

I have noticed the issue on the Mac mini M1 with Dual displays using HDMI+USB-C to DisplayPort and HDMI+USB-C to HDMI. However I was able to remedy it by shutting off both displays and powering them back on once the Mac is at a logon screen.

I did NOT run into an issue when I used HDMI+DisplayPort to miniDP on a CalDigit TB3 dock.

Hopefully the issue is graphics driver related and can be fixed with an update.

Hardware: 2020 Mac mini M1 /w 16GB RAM + 1TB HDD, 2 BenQ U2700D Monitors

I *THINK* I have resolved my issue. I had 2 BenQ monitors with HDMI only on them. I've just changed them for 2 other BenQ monitors which had both HDMI and DisplayPort.

Got one using HDMI and the other using DisplayPort and so far it seems to be working.

I have noticed some odd pink squares appear which at boot up though.

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.

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)

I had the same problem and on this site, I read that someone had no problem with a VGA to USB C adapter , so I bought one from Amazon : Belkin USB C to VGA adapter. I received today the problem is fixed works perfect with my LG low cost monitor

Good luck

A reasonably good analysis, Alastair Houghton. Thank you.

Another issue, in the mix, is that the “USB-C” connectors, on the M1 Macs—the ones with the Thunderbolt symbol—are actually USB4—the newest USB standard.

This new standard has its own “wrinkles”, with regard to various modes.

They are not to be confused with the old USB-C/Thunderbolt-3 ports on the Intel based Macs.

The main thing that will take time to catch-up to this change are the adapters and cables: there are, at least, three levels of cable compatibility, all with their own logos, which are supposed to help consumers know they have the correct products.

However, I have yet to see these logos displayed where they should be, let alone on sites where one may order such—even from Apple.

This is not, truly, the fault of Apple’s M1 based Macs—Apple is simply making this change contemporaneously with the M1 change, in order to be prepared for the future.

Unfortunately, however, the rest of Apple—let alone the rest of the computer industry—has yet to catch-up to this (coming) future.

For some time I have been surprised by all the problems people have reported getting monitors to work with the M1 Mac Mini. I attributed them to the possibility that people in some countries may have received ‘Monday production’, or some such. Why? Because I experienced no trouble connecting two monitors, and - after a lot of trial and error - now have three monitors working with a 16 GB Mac Mini, in a flight simulator running X-Plane.

Note that my monitors are relatively inexpensive and ‘old’. If it will help anybody, here are the details:

One monitor is actually a Westinghouse TV model LDD2240 (1920 x 1080 @ 60 Hz), and it is connected via HDMI to HDMI.

The second monitor is a Flatron W2252TQ connected via VGA on the monitor to a Belkin VGA/Thunderbolt adapter to a Thunderbolt port on the Mac Mini.

The third monitor is a Dell model 2007 FPS (1600 x 1200 @60 Hz) connected via VGA on the monitor to VGA/DVI-I adapter to Startec.com’s ‘USB 3.0 Dual Head Graphics Adapter’ to USB-C on the Mac Mini. This required a free DisplayLink driver to be downloaded from Startec’s website, and then turned ‘on’ in the Mac Mini.

I have switched the connections between the second and third monitors, since both are VGA, and there was no problem either way.

Do all three monitors light up immediately when the computer is turned ‘on’? No, sometimes there is a very slight delay, but as soon as I activate X-Plane, all three light up.

The first time I used the Startec device, the Mac Mini saw all three monitors, but X-Plane still only saw two. My wife suggested that the program was acting like a spoiled child and did not want another monitor to come into the ‘house’, so I went into System Preferences and designated the 3rd monitor to be the ‘main monitor’. (Who is a big boy now?). That did the trick, and X-Plane saw all three monitors. When I went back through System Preferences and redesignated the monitors to their proper positions, all three were active on X-Plane. It was as though ‘introductions had been made and the proprieties observed’.

Don’t challenge me on the logic of my explanation. Computers are smart and the program uses Artificial Intelligence, so maybe they can no longer be treated like adding machines. As Ann Landers used to say, “If it happens, it must be possible.”

One final point: The Startec device cost $83 and their support was excellent. I would not have known about the driver without it.