Extending 2020 MBP screen to iMac

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Extending 2020 MBP screen to iMac

Hi Apple Community! I am trying to extend my 2020 MBP screen to a 27" iMac. I was able to do this with an older (2015) MBP and a Thunderbolt 2 cable connected to both. Now, I am using a Thunderbolt 2 cable from an iMac (identifier13,2) running 10.15.6, to a Thunderbolt 3 to Thunderbolt 2 Apple Adapter (MMEL2AM/A), connected to my new MBP (identifier 16,2) running 10.15.6. Using CMD-F2 (as before) does not extend the MBP display onto the iMac.

Any ideas how I can use that massive 27" iMac real-estate from my MBP?

Thanks

MacBook Pro 13″, macOS 10.15

Posted on Jul 22, 2020 8:48 AM

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Answer 1

Jul 23, 2020 6:34 AM in response to richbrazil

I am very much surprised, but since you say you are 100% sure I cannot contradict you.

I am surprised because this document says it won't work:

https://support.apple.com/en-us/HT204592

I found a thread where a big contributor to this forum suggested it would work, but the document he linked to has been removed.

It seems that even if it does work in some cases, it is alas not a supported feature.

You could try creating an installation of High Sierra on a separate drive, and check if the functionality is restored when booting into that OS.

You can still get High Sierra from Apple:

Get macOS High Sierra

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Answer 2

Jul 22, 2020 9:12 AM in response to richbrazil

What OS is running on the iMac?

If the iMac is running Catalina, it won't work as target display. I believe it was Catalina that removed that functionality of older iMacs; it could be Mojave, I am not absolutely sure.

EDIT: I see now that VikingOSX beat me to it. So it needs to be High Sierra or earlier.

I know for a fact that with High Sierra it works. Been there, done that (fortunately or not, my 2011 iMac can't go past High Sierra, and it continues to work great as a display).

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Answer 3

richbrazil Author

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Jul 22, 2020 5:39 PM in response to Luis Sequeira1

Luis Sequeira1: thank for reply, and appreciate the help and time.

I am at a total loss here, since the last time I was able to CMD-F2 and get my MBP (2015) to mirror onto my iMac (2012) - both were running Catalina 10.15.5 at the time - 100% guaranteed this was the case. The only critical thing was that the receiving iMac (2012) had to be on the logout/login screen, or the mirror CMD-F2 would not work/would not be recognized. It's driving me crazy that I cannot get this to work.

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Answer 4

richbrazil Author

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Jul 24, 2020 3:46 AM in response to Luis Sequeira1

Luis Sequeira1

Thank you for your references and help.

I think I have reached the tough point where my iMac will not work for this - downgrading to High Sierra is not feasible at this time. Wish I knew how this worked less than 30 days ago ...

Thanks again!

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Answer 5

Jul 22, 2020 9:05 AM in response to richbrazil

Your 2012 iMac must be running High Sierra 10.13.6 or earlier to support Target Display Mode from your MBP.

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Answer 6

richbrazil Author

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Jul 22, 2020 9:42 AM in response to VikingOSX

Thanks VikingOSX.

Before upgrading to the 2020 MBP, I had successfully extended from a MBP Retina early 2015, running same OS on both machines... not sure why this new MBP won't extend....

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Answer 7

Jul 22, 2020 9:46 AM in response to richbrazil

Same OS? Which one?

What OS is running on the iMac? That is the key thing.

Your new MBP is running Catalina, obviously, and that is fine, but the iMac must not be running anything later than 10.13.6.

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Extending 2020 MBP screen to iMac

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