Problem with 2nd Monitor and 2 computers.

[joker00]

I seem to have a problem when using the Studio Display with a second monitor and 2 computers.
My main display is the SD, I have a second monitor that also plugs into my Mac Studio (thunderbolt to DP cable).

When I switch the 2nd monitor's input to choose the 2nd computer, the Mac Studio still thinks the 2nd monitor is connected...it shouldn't. what ever app was on the 2nd monitor should have moved to the SD.

 

[Spanky Deluxe]

That’s nothing to do with the studio and is entirely based on how your display works. It’s not sending a disconnected signal to your monitor. I have a real problem with my current Mac but the other way around; if I’m using my second monitor with my PC but the screen goes to sleep, it still sends the disconnect signal to my Mac, which means all my windows and icons get messed up. It’s infuriating! I had to get a dummy HDMI plug that is set up to mirror the display to lessen the issue but it still happens at times.

 

[edanuff]

I think it’s the monitor. I have the same thing happen with the two Dell U2720Q monitors I have hooked up to my Mac Pro 6,1. One of the monitors is shared with a PC but when I switch input from the Mac to the PC, the Mac still sees it. I then have to manually go to the Mac display preferences and set it to mirror the displays to not have a bunch of windows and apps offscreen.

 

[Chancha]

Yes it is entirely dependent on how your 2nd display is programmed by its manufactuer. Some times you can change the connection from DisplayPort to HDMI and that display will change its behaviour, or it may not, it is almost random.

I don’t think you can have a reliable solution to this without physically unplugging that DP cable.

 

[joker00]

Yes it is entirely dependent on how your 2nd display is programmed by its manufactuer. Some times you can change the connection from DisplayPort to HDMI and that display will change its behaviour, or it may not, it is almost random.

I don’t think you can have a reliable solution to this without physically unplugging that DP cable.

some good point.
I should mentioned before the Studio Display, my mackintosh didn't have this problem.
the mackintosh did have DP to DP connection, but not I use a cable to connect DP (monitor) to TB (Mac Studio).
My guess the monitor does a disconnect, but it's being lost in the cable.

 

[Chancha]

My personal anecdote is that HDMI is more prone to re-initiating a handshake, thus we hear all sorts of blackout or flicker issues with HDMI, but concerning this discussion the handshaking actually keeps the computer from seeing the display once the display is off or even just switched input to something else. While DP is a more reliable connection in the PC world, thus it usually stay connected regardless what's happening on the display, therefore macOS persist to use it as part of the extended pool of displays despite you are not actually seeing the image on there. But I am only describing the general assumption, it can easily be some other case for any given setup.

In my line of work, I used to be a techie in a music studio and now a management for another music related publication, because of the aforementioned behaviour, I tend to never have displays doing double-duty specifically to avoid this "channel changing" problem. The time loss in trouble shooting or even down time is not worth it, just add displays physically if there are really so many machines that need it.