You can make a difference in the Apple Support Community!

When you sign up with your Apple Account, you can provide valuable feedback to other community members by upvoting helpful replies and User Tips.

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

Problems using TWO identical external monitors with my 2021 16" MBP M1 Max (clamshell mode)

Just got my new 2021 16" MBP with M1 Max setup and everything was working well until I got around to my final task of hooking up my external displays! I am currently running Monterey 12.1 on my MBP.


I have two brand new and identical Dell 27" 4K (S2721Q) monitors that I am trying to hook up to my MBP and run side by side with the MBP in clamshell mode. One monitor is connected with HDMI-to-HDMI and the second with HDMI-to-USBC. My MBP is connected to power with the Apple power adapter via MagSafe.


When trying to connect displays, this is what I CAN DO:

  1. Mirror MBP to one display (both with lid open or in clamshell)
  2. Use MBP with lid open and extend to one external display


The "non-functional" monitor does in fact work because it turns on and will sometimes show a messed up video feed of my screen for a couple seconds (with the other monitor showing everything fine) before cutting out again. I also will occasionally get an error message on the monitor saying that "the current input timing is not supported by the monitor" although both monitors are identical and the other works without any issue!


I am reading on other forums that there are lots of connectivity issues for two monitors with the new MBP on Monterey but I'm sensing that my issue is a little different. I also noticed that the "Displays" section of System Preferences is not like it used to be in previous versions of OS so maybe I'm doing something wrong too...


Maybe it's fatigue or something I'm not seeing but I am stuck!! Any help, tips or insight is appreciated!

MacBook Pro 16″, macOS 12.1

Posted on Jan 9, 2022 8:02 AM

Reply
Question marked as Top-ranking reply

Posted on Jan 9, 2022 11:15 AM

4K @ 60Hz is the upper limit of what can be supported by HDMI 2.0, a recent standard supported by the HDMI-direct port on the most recent M1 MacBook Pro models.

NB> cables that are certified as premium high-speed cables are required for trouble-free operation.


60Hz is not supported by that cable/adapter.

You could try 30Hz, it might work. Or you could look for a better cable/adapter.



Similar questions

10 replies
Question marked as Top-ranking reply

Jan 9, 2022 11:15 AM in response to paris514

4K @ 60Hz is the upper limit of what can be supported by HDMI 2.0, a recent standard supported by the HDMI-direct port on the most recent M1 MacBook Pro models.

NB> cables that are certified as premium high-speed cables are required for trouble-free operation.


60Hz is not supported by that cable/adapter.

You could try 30Hz, it might work. Or you could look for a better cable/adapter.



Jan 9, 2022 10:21 AM in response to Grant Bennet-Alder

The HDMI-to-USBC connection is the one that does not work. In System Preferences, I see my MBP and the two external monitors appear in the distribution and list of displays but no feed is sent to that second connected monitor. This is the monitor that gives me the error message "the current input timing is not supported by the monitor" (see photo). From time to time, I will briefly get a messed up feed (see other photo) but that will disappear to show the same error message again.


I have tried swapping connections, even using different cables and ports to make sure that wasn't the issue. No change.

Problems using TWO identical external monitors with my 2021 16" MBP M1 Max (clamshell mode)

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.