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UnlikelyLass

macrumors member
Original poster
Mar 28, 2016
38
26
I have an inexpensive external monitor with both USB C and HDMI inputs. It’s even got HDR — but its resolution is 1080p. Although I could previously use it as an extended external monitor with my M1 iPad Pro, I now can only mirror. This appears to have started recently. I believe I can still use a 4K monitor to extend onto, but I’ll re-test later today.

Has anybody else seen something like this? I found a few random threads of something similar happening around 16.3 that was fixed with 16.3.1, but no mentions with 16.4.
 

teh_hunterer

macrumors 65816
Jul 1, 2021
1,111
1,450
I have an inexpensive external monitor with both USB C and HDMI inputs. It’s even got HDR — but its resolution is 1080p. Although I could previously use it as an extended external monitor with my M1 iPad Pro, I now can only mirror. This appears to have started recently. I believe I can still use a 4K monitor to extend onto, but I’ll re-test later today.

Has anybody else seen something like this? I found a few random threads of something similar happening around 16.3 that was fixed with 16.3.1, but no mentions with 16.4.
Have you turned on Stage Manager?
 

arfung

macrumors member
Jun 27, 2015
85
34
And, when the external monitor is connected, you might need to go to Settings -> Display & Brightness and turn off mirror to external display.
 

UnlikelyLass

macrumors member
Original poster
Mar 28, 2016
38
26
I have stage manager turned on. I have a pointing device and keyboard connected. This feature has worked, with these settings and this monitor previously, but now only mirrors.

Further debugging has happened — I have access to 2 M-class iPads and both have the same behaviors:

  • With a 4K monitor with USB C connection, works for both iPads with either USB C or HDMI inputs
  • With a 1440p monitor with only HDMI inputs, works for both ipads
  • With a 1080p monitor with only HDMI inputs, works for both ipads
  • With *this* portable 1080p monitor, does not work with either USB C or HDMI iPad for extended display, defaults to mirror only. Interestingly, the monitor reports it’s current resolution to be 1440x900 (although Max is display as 1920x1080)
I also have an M1 MacBook Air and a raspberry pi.

With the pi, the monitor works, and defaults to 1080p

With the MacBook, the monitor works as an extended display OR a mirrored display. But it also adopts the resolution of 1440x900 and marks it with (default) in the resolution list. Because this is supported in MacOS, I can increase the resolution to the available maximum — 1080p — without trouble.

So, I *think* what has happened is that iPadOS has implemented two things:

1. (Possibly new) It only uses the monitor-reported default resolution, not maximum resolution and
2. (Possibly new) a minimum resolution for extended display support, which is 1080p. If your reported default is not 1080p or higher, extended display support (NOW) doesn’t work.

Either or both of these might be new. One or both previously weren‘t the case, as previously this very same monitor worked for extended display on my m1 iPad Pro and now it reliably doesn’t.

Dunno. Just a theory, but it seems to match the behavior.
 

UnlikelyLass

macrumors member
Original poster
Mar 28, 2016
38
26
Additional weird detail: this monitor, when plugged into an INTEL MacBook Pro running the same version of ventura defaults directly to 1080p.

My best guess is that some low level apple Arm gpu driver behavior has changed w/r/t how it parses or identifies this specific monitor — and in macOS it at least allows me to override it’s incorrect default, but in iPadOS that’s not permitted. And for whatever reason, 1080p seems to be a lower limit for enabling external display support.
 
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