Why does the target display mode stop working? It was working just last week

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77mak77 Author

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Why does the target display mode stop working? It was working just last week

Nothing had changed, but I am unable to use my old imac as a display all of the sudden? Please help.

Posted on Aug 16, 2023 5:08 PM

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Answer 1

Aug 16, 2023 7:03 PM in response to 77mak77

What Macs are you using Target Display Mode with? (Model and year from About This Mac in the Apple () menu)

Which Mac is running in Target Display Mode, serving as "the screen"?
Which Mac is displaying its output on the other Mac?
How are they connected? Via Mini DisplayPort, or via Thunderbolt?

Do they meet all of the requirements for Target Display Mode, including the very restrictive ones that Apple added on "the other Mac" (must be from 2019 or earlier, must be running Catalina or earlier)?

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Answer 2

77mak77 Author

Level 1

4 points

Aug 16, 2023 9:01 PM in response to Servant of Cats

It meets all the requirements, I use my 2010 imac as the secondary screen and 2019 imac (now updated with the Ventura). Before the update which was last week, it worked perfectly fine for the last three years, could it be the software update that disable TDM?

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Answer 3

Aug 16, 2023 9:26 PM in response to 77mak77

Your 2019 iMac no longer meets the requirements, because it is running Ventura, which is later than Catalina.

i don’t care for (and didn’t expect) the restrictions on the new Mac, either. I have a 27” Late 2009 iMac that until recently, was still going strong.

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Why does the target display mode stop working? It was working just last week

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