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My iMac(s) failed to recognize external monitors (iMac 27 or MacBook Air).
Following the instruction: System Preference > Displays > Option & Detect Displays
But nothing happens. I have tested all three iMacs and a MacBookAir and trying to connect them, but no luck. What is preventing me from going past this issue?
iMac 27″ 5K, macOS 11.6
Target display mode is a feature that was available only with certain older iMac models.
Only the following older iMac models can be used as an external display when plugged into another older Mac model:
Please read this carefully > Use your iMac as a display with target display mode - Apple Support
Also know that TDM has been deprecated and abandoned by Apple since 2014. No macOS newer than Catalina supports it, and no hardware newer than 2019 supports it.
Target display mode is a feature that was available only with certain older iMac models.
Only the following older iMac models can be used as an external display when plugged into another older Mac model:
Please read this carefully > Use your iMac as a display with target display mode - Apple Support
Also know that TDM has been deprecated and abandoned by Apple since 2014. No macOS newer than Catalina supports it, and no hardware newer than 2019 supports it.
Thank you, D.I. Johnson. This is a very very helpful article you wrote. I am very thankful for this. One question, or concern I have is what kind of issue might I have with the source iMac if I were to downgrade the OS to 10.15 Catalina or earlier version (I assume these are 32bit platform/) from macOS 11.6 Big Sur, or 12.4 Monterey which are 64bit based platform. Would I have any issue with running updated apps on my source iMac(s) that are setup for 64bit platform?
If that is the case I am not sure if it is worth plugging an old iMac to be used as a dual display.
What do you think?
Target display mode is tricky.
You need to follow this to the letter:
Use your iMac as a display with target display mode - Apple Support
Catalina was the first all-64 bit operating system. So that is not an issue. As to whether you should do it, that is totally up to you.
Trying to make a dual monitor arrangement for my iMac 27" with other iMac 27s (or to a MacBook Air) without success
