Does anyone have trouble with their Macbook recognizing an external display? I have a new 2020 Macbook Pro and it struggles to recognize my Samsung display. I often have to reboot the Mac for it to be recognized.
I’ve got issues where macOS sees both monitors but won’t send output to both every time I come out of sleep. Like one of the displays will turn on like it has signal, then hang for a second and go back to sleep, repeat. I use a program called disable monitor, which shows all the profiles for the display. For some reason when one doesn’t connect it goes into the first profile for the resolution/refresh rate/color depth, then I manually select the third and it connects right away
I wonder wether there's some problem with the usb-c alternate modes and their implementations / drivers.
Below are a bunch of my experiences with this which shows that behaviours are all over the place which kind of excludes an outright broken OS or piece of equipment. To me it looks much more like a compatibility issue.
I don't own a usb-c mac, but I've never had any problems whatsoever with my 2013 retina, always works perfectly even with 4k@60Hz screens.
I have a desktop PC which exhibits the same kind of weird behaviour you have. It has a thunderbolt 3 / usb-c / dp connector which is downright awful.
I've managed to connect an Apple thunderbolt display to it with official tb2 -> tb3 adapter, it works well most of the time. Put the computer to sleep though and the screen never comes back on. Sometimes it doesn't detect the USB ports on it either. Mostly works if I force the thunderbolt mode to DisplayPort only in the bios.
I've next connected a regular usb-c monitor to it (DP alternate mode + usb2 for peripherals). Works great in bios. Mostly works on Linux. On windows it turns off when getting to the login screen. I don't know how, but I've managed to get it to work exactly once. When I turned the computer back on the next morning, it was again off on the windows login screen. The monitor IS detected, it shows up in the Display Preferences if I connect it to both usb-c and display port. It just won't turn on.
On Linux, it kinda works. I would say there's a 50/50 chance it won't detect it at 60 Hz. Sometimes, if it works at 60Hz, if the display goes to sleep it won't come back on at 60Hz. I guess at least there is some output, so it's got that going over windows.
I found an option on the bios to enable "high speed display output". No idea what exactly that means, it didn't do anything.
This same screen works perfectly with a usb-c (no thunderbolt) laptop on linux. Never had any issue, always detected as 4k@60Hz.
