Target Display Mode operating system compatibility

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Level 1

4 points

Target Display Mode operating system compatibility

Hi all,

I've seen a bunch of these types of questions asked previously, but none quite addressed my query...

I have a 2020 (intel) iMac running Catalina that currently uses TDM to have an extended display onto a Late 2009 iMac running High Sierra. As is, this works fine, but I want to upgrade from Catalina to Monterey on on my newer iMac, as some of the software updates are now moaning it's a bit old. I also have a few niggles (like an odd Finder issue) that I want to flush out with an update.

From what I have read here, this current (working) combo should not even be working (my Catalina iMac is clearly newer than 2020). I am not using Open Core Legacy Patcher (or anything other non-native approach to achieve this).

Does anyone know if I upgrade from Catalina to Monterey if this will still work in TDM?

I did a quick test on a MacBookPro running Ventura and TDM seems to work fine to my 2009 iMac (USB-C to mini display port). I assume therefore, if it works on a later OS it will work on the one before, but just want to be sure before I commit!

Cheers

BlueSofa

[Re-Titled by Moderator]

iMac, macOS 10.13

Posted on Apr 25, 2023 9:49 AM

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Answer 1

Best reply

Limnos

Level 10

412,501 points

Apr 25, 2023 9:53 AM in response to BlueShrew

According to the documentation, Monterey will break it. If you say you got it working with Ventura then it seems you got lucky with something (and we can't guarantee a repeat), but officially here's what Apple says:

Review the document: Use your iMac as a display with target display mode - Apple Support

Target display mode is a feature available with late 2009-Mid 2014 iMacs. The display Mac has to be running macOS High Sierra or older and the signal producing Mac has to be running macOS Catalina (ca. 2019) or earlier.

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Answer 2

dave2.0

Level 1

10 points

Apr 12, 2024 6:53 AM in response to BlueShrew

I own two imac2010 27inch and use them as external displays for my work setup. I did not encounter any problems using it with my macbook air m1.

I habe connected the imac via dell wd15 docks. it works like a charm.

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Answer 3

BlueShrew Author

Level 1

4 points

Apr 26, 2023 3:02 AM in response to Limnos

Well, I did a test by installing Monterey onto a USB3 HDD and booting the 2020 iMac from this source. It took forever (it was a spin disk after all), but it worked. Once I hit CMD+F2 on the 2009 iMac (running High Sierra) I got an extended display in Monterey over the mini display port cable (as before with Catalina) with no third-party add-ons or other tweaks, see attached.

So if I got lucky with Venture by trying this from an M1 Mac, I also got lucky on the older 2020 iMac, which seems a bit of a coincidence. Either way, there appear to be at least two combos of hardware and OS where TDM still seems to work. It would be interesting to hear of anyone else with the same/similar hard ware getting the same result or if I am just lucky (twice)!

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Answer 4

dialabrain

Level 10

122,891 points

Apr 26, 2023 4:33 AM in response to BlueShrew

My guess is you got lucky twice. I remember reading somewhere there were different 2009 iMacs, different hardware, one would work, one wouldn't.

Since I don't have any Late 2009 iMacs I can't test them to verify.

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Target Display Mode operating system compatibility

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