Since upgrading to Monterey 12.3 my Mac mini (2018) does not boot up to my single USB-C display. (LG 27UK850). It would find a HDMI display. So I have had to reconnect my display using HDMI. This is a bit of a nuisance. Why can't I simply connect the display using USB-C, as I always used to?
Mac mini 2018 or later
Here is similar issue that was fixed by an LG port setting:
Mac Mini won't wake up after 12.3 update - Apple Community
It appears many have had monitor issues with 12.3. Mostly dual monitors where one does not work. The only fix was for them to downgrade back to 12.2.1.
After Monterey 12.3 upgrade, can't run 2 … - Apple Community
What is it really using for video input, DisplayPort or Thunderbolt. The USB-C port supports Multiple protocols. macOS doesn’t support video over USB. If it is a USB video input, you must have used a third-party extension to push video over USB. That probably doesn’t work under the new OS.
Thunderbolt 3 is the main standard source for display output, and it uses the same physical connection as USB-C. I usually refer to these ports as USB-C,
The form factor of the port is USB-C, but it supports multiple protocols as I stated in my original reply.
but perhaps should have called them called Thunderbolt 3 (which, I understand, is also an advanced form of DisplayPort)
It is not. The ports support USB, Thunderbolt, and DisplayPort, as I already stated. There are some monitors that can connect to the video bus over USB.
For years I have happily used my Mac mini with a single cable connecting one of its USB-C (ie Thunderbolt 3) ports to my LG display monitor. When it booted up the display appeared and worked. No third-party software was involved.
Finally, the answer to the question I asked, I think. You connect it to the Thunderbolt port on the display? Or is it the DisplayPort?
But now, with Monterey 12.3, the display doesn’t appear if it is connected to one of the USB-C ports. The only way I can get it to work is to use an HDMI connection.
Does it appear on the Thunderbolt video information in System Information?
I’d be interested to know if this is a general experience with 12.3. During upgrading the process stalled a few times and took forever. Perhaps there is something wrong with RAM settings on my Mac mini?
From what OS did you upgrade. I have used Monterey to connect to a display over TB2, but I don’t, currently.
Very interesting, thanks - but my LG monitor offers very limited choice of port settings: if we select the physical input port as USB-C then there is an option in the monitor's settings to enable or disable DisplayPort 1.2. My monitor has always (I think) had this setting enabled, which seems sensible and I'm not inclined to change it! (There's no mention of 1.4 on this model)
Meanwhile, looking back at the system information in the Mac mini (2018), there doesn't seem to be any mention of version of DisplayPort. It seems to me that the information given on Thunderbolt 3 has been deemed to replace DisplayPort. (And, of course, this Mac mini doesn't have a physical DisplayPort socket)
Thanks, Barney, but maybe I didn’t explain properly. The Mac mini (2018) has 4 USB-C ports that are also Thunderbolt 3. Thunderbolt 3 is the main standard source for display output, and it uses the same physical connection as USB-C. I usually refer to these ports as USB-C, but perhaps should have called them called Thunderbolt 3 (which, I understand, is also an advanced form of DisplayPort).
For years I have happily used my Mac mini with a single cable connecting one of its USB-C (ie Thunderbolt 3) ports to my LG display monitor. When it booted up the display appeared and worked. No third-party software was involved.
But now, with Monterey 12.3, the display doesn’t appear if it is connected to one of the USB-C ports. The only way I can get it to work is to use an HDMI connection.
I’d be interested to know if this is a general experience with 12.3. During upgrading the process stalled a few times and took forever. Perhaps there is something wrong with RAM settings on my Mac mini?
The user doesn't actively choose the display protocol; s/he plugs a cable into a hole in the Mac mini. This simple user (me) plugs a USB-C cable into one of the four USB-C (Thunderbolt 3) ports on the Mac mini (2018). The other end of the cable is plugged into the USB-C input of a LG monitor.
I generally update the OS software when an update is offered. In this case I think that the previous OS was 12.2.1
Previously the display has always been automatically recognised. Now (with Monterey 12.3) it isn't.
My setup is very straightforward, and must surely be used by thousands of others. A single USB-C monitor is connected to one of the Mac mini's USB-C ports. So I should like to know whether this new failure to recognise my display is a "feature" of Monterey 12.3. If not then there must be something wrong with my Mac mini.
So, your LG display randomly changes the video protocol it uses, and you have no idea which one it is using?
mac mini boot not to USB-C display
