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

Two Monitors working on a Mac Mini M1 16gb

I have a successful set up. I bought the mac mini with 2 - BenQ PD2700U and a OWC Thunderbay 4 (thunderbolt) which also has a DisplayPort 1.2 port at the back.

I have a HDMI connected directly to one of the monitors. The thunder bay is connected to the Mac Mini M1 via the included thunderbolt cable and the second monitor is connected to the DisplayPort 1.2 port in the back of the Thunderbay. I am using no adapters anywhere and all cables are relatively short. Less than 1.5metres.

It works perfectly, wakes from sleep without issue. Have not had to restart I have the set up 4 days already and I work all day on the machine. On another note I do fid some blue tooth glitches, hanging etc. I am running the latest Mac updates as of 20th Feb 2021.

I hope this helps someone.

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.

Public 11.1 is available for download 12/15/2020. Check update.

Did you upgrade to 11.1? It greatly improved the problem for me.

Don’t think so. My monitors were both 1440p and had the issue. However it was resolved after a clean install of the OS. Other issues persisted so it was ultimately returned anyway.

I use the hdmi to hdmi as my primary monitor and usc-c cable which goes to my monitor which uses DisplayPortbover USB-C. It was not working on 11 or 11.1 but now fully works on 11.2

Same problem as all of you. I was on phone with Apple Support and it said that with 2 monitors we have to use the 2 thunderbolt output, not mixed with hdmi output. We saw that it's not what it is indicated on the Mac mini specification page, so the advisor was little confused. I said I test that solution to see...

Does anyone of you already made the test ?

My assumption would be more in the direction of software (Big Sur), since after dis- and reconnecting the HDMI cable from/to the HDMI port or alternatively changing the display resolution to something other than and back to the native resolution everything works pretty well. So my guess would be that the hardware itself does work.

I've also run into this issue. Upon rebooting, I've found that it changes the refresh rate on one of the displays (which can be changed back in the settings) and it changes the order of the monitors so i have to scroll the long way to get between monitors. I use it with two Samsung 27" monitors with the refresh set to 144 for each, but after rebooting, one of them changes to 60.

Thanks for pointing that out. I just checked my display information and as you said it seems like I my new monitor's refresh rate is working @ 30Hz instead of @ 60 Hz (Please see the attached screen shot). To be honest, I am not familiar with these hardwares so I didn't know what to do to solve this and the reason why I am trying to get a USB C to Displayport cable is because I found this Youtube video reporting a similar issues: https://www.youtube.com/watch?v=ZbJXETn0PuY

This guy had the exact same monitor and issue and went around the it with replacing HDMI with Displayport cable. It seems many more experienced the same issue and solved it with the same approach, as shown in the comment section.

I checked the j5create cable, but it says it's 4K compatible with 60 Hz refresh rate.

This one advertises 1.4. StarTech.com 6ft/1.8m USB C to DisplayPort 1.4 Cable - 4K/5K/8K USB Type-C to DP 1.4 Alt Mode Video Adapter Converter - HBR3/HDR/DSC - 8K 60Hz DP Monitor Cable for USB-C/Thunderbolt 3 (CDP2DP146B) https://www.amazon.com/dp/B07VN6B5GR/ref=cm_sw_r_cp_api_glc_fabc_b7l0FbCRP1CTF

Ok, I’ve done a ton of troubleshooting, and so far I’ve gotten it fixed as best I can tell. I wiped the drive completely clean, and reinstalled Big Sur. This in itself had bugs which required workarounds to actually work... but once it was done, so far I can’t trigger the issue like I could reliably before. This new installation is NOT 11.1, it’s still running 11.0.1. And I have a strange theory as to why it worked, could be totally wrong...

I got a popup earlier that welcomed me and offered a tour of my new MacBook Air... on my Mac Mini. I’m wondering if this is even possible, that when they flashed some machines, they accidentally installed some firmware or SOMETHING more relating to the MacBook Air.

”About This Mac” always showed it being a Mac Mini, but that pop up has me suspicious that something funky happened during manufacturing and flashing the OS on some machines, which was fixed when I wiped it and reinstalled.

I’m not formally educated in any of this, but I feel like this theory is at least possible... anyone smarter than me have any thoughts?

Has anyone taken these same steps without success?

If it anything like the problem I had, Apple may come back because of the actual wording of the technology. Looking at the LG website it reads:

> Offering a new generation of convenience, USB Type-C™ports allow 4K video display, data transfer and laptop/mobile device charging, all at the same time over a single cable. Reduce cord clutter and increase efficiency with USB Type-C™.

(https://www.lg.com/us/monitors/lg-32UL750-W-4k-uhd-led-monitor )

and as you pointed out you have one monitor connected via the thunderbolt port and one via HDMI.

Problem is that whilst USB-C is the same connector type as thunderbolt, it’s not actually thunderbolt.

I had the same issue with Apple’s own sold A2119 multi-display adaptor. Engineering told me that it’s a USB-C adaptor so it’s not a supported accessory to run dual monitors. As a single monitor out, it’s fine and supported, but not for two monitors.

Hello WOStudio,

I understand your frustration, but for me, I temporarily fixed by using VGA cable , I know it is old style but it works ? so I have one screen on HDMI and the other screen with USB-C adapter to VGA cable , it is perfect. I had before adapter USB-C to HDMI and it doesn't work - I don't know why ? so I when to the easiest way ....

Good luck ,

Claude