Target Display Challenge

Question

Level 1

8 points

Target Display Challenge

Hi There,

I've been battling to enable Target display to work and hope someone can point me in the right direction. I have a Late 2012 iMac which was running on the latest Mac OS (Big Sur). Based on the articles in this site, I downgraded to High Sierra 10.13.6 as my understanding is that it is the latest version that supports the Target Display functionality. I have a MacBook Pro 15" mid 2014 running on Big Sur and have tried several cable combos with no success:

Thunderbolt - HDMI (brand new cable with no converters)

Thunderbolt - Thunderbolt (converter on the laptop)

Thunderbolt - Thunderbolt (converter on the imac)

I have double checked keyboard settings, system settings and even connected an external screen to my iMac to see if the Tunderbolt ports may be damaged but that worked fine. The only possible clue I have found is in the Apple System Log (ASL) Messages, when I invoke the CMD+F2 combo which should switch the iMac to Target display mode, it records what looks like related errors as follows:

10 Jan 2021 at 10:01:25 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

10 Jan 2021 at 10:01:31 com.apple.xpc.launchd[1]: Service exited due to signal: Killed: 9 sent by mds[60]

10 Jan 2021 at 10:01:35 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

10 Jan 2021 at 10:01:45 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

10 Jan 2021 at 10:01:55 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

10 Jan 2021 at 10:02:05 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

10 Jan 2021 at 10:02:07 dpd[166]: objc[166]: __NSArrayI object 0x7fdb4de18220 overreleased while already deallocating; break on objc_overrelease_during_dealloc_error to debug

10 Jan 2021 at 10:02:15 dpd[166]: objc[166]: __NSArrayI object 0x7fdb4de18220 overreleased while already deallocating; break on objc_overrelease_during_dealloc_error to debug

10 Jan 2021 at 10:02:15 com.apple.xpc.launchd[1]: Service only ran for 0 seconds. Pushing respawn out by 10 seconds.

Can anyone please easy my pain and tell me if I am doing something wrong or why this is not working?

Thank you

Posted on Jan 10, 2021 2:21 AM

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Answer 1

Jan 12, 2021 10:56 AM in response to borislav77

Hey there borislav77,

We'd like to help get your iMac to work as an external monitor while using target display mode.

While this article is no longer updated by Apple, we wanted to provide the steps to take under 'If target display mode doesn't work' here: Use your iMac as a display with target display mode

If you need more help, we recommend reaching out to Apple Support here: Get Support

Have a good one!

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Answer 2

Jan 13, 2021 1:26 AM in response to borislav77

Is it really a 2012 iMac? You said it had been running Big Sur, but Big Sur won't run on an iMac older than 2014.

You can't use a HDMI port, cable, or adapter for Target Display Mode. You need a Thunderbolt cable, no adapters or converters.

Apple Thunderbolt Cable (0.5 m) - White - Apple

Apple Thunderbolt Cable (2.0 m) - White - Apple.

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Answer 3

Jan 13, 2021 3:43 AM in response to borislav77

The no adapters/converters rule is to keep the connection all Thunderbolt. The Apple Thunderbolt 3 adapter is all Thunderbolt, so is not a problem. Your work machine being 2020 is a problem, and it cannot use any Thunderbolt iMac as a display, no matter which cables or adapters are used

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Answer 4

Jan 13, 2021 3:34 AM in response to borislav77

You can connect to Mac that has Thunderbolt 3/USB-C using a Thunderbolt cable and a Thunderbolt 3 adapter

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple

but not to a 2020 Mac.

Use your iMac as a display with target display mode - Apple Support

"You can connect any of these older iMac models to another Mac from 2019 or earlier for use as an external display."

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Answer 5

borislav77 Author

Level 1

8 points

Jan 13, 2021 3:01 AM in response to Malcolm J. Rayfield

Hi Malcolm,

Thanks for your feedback. my iMac is definitely Late 2012 and I could be wrong about it running big Sur but it was a version later than the one specified in the article TDM mentioned works so I think I had to downgrade to try this regardless. In terms of the cable, this may well be the problem and I will get one to try with my current personal laptop but with the newer MacBook pros not having Thunderbolt ports (my work machine is a 2020), does that mean I cannot connect it to a MacBook that only has USB C ports?

Regards,

Boris

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Answer 6

Jan 13, 2021 3:10 AM in response to borislav77

USB C is the size and shape of the connector, just like USB A and USB B etc. The signal carried over the wire and through the connector on all newer iMacs is Thunderbolt 3. Thunderbolt 1 and 2 used MiniDisplay Ports (MDP) while Thunderbolt 3 and 4 are using USB C connectors and ports. I hope this helps.

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Answer 7

borislav77 Author

Level 1

8 points

Jan 13, 2021 3:35 AM in response to Jeff Donald

Hi Jeff, Yeah I get that, just wanted to understand what looks to be a bit of a conflict in my mind, on the one side, one should use a cable with no converters (as suggested above) but on the other side of the coin, you say USB C vs Thunderbolt is just a different connector (endpoint of the cable). So with this in mind, I would prefer to ensure this would work before I buy more cables, converters etc.

Let's say I get the Apple Thunderbolt Cable mentioned by Malcolm above and this works connecting my Mid 2014 MacBook Pro to the Late 2012 iMac. In order to connect the iMac to my work machine which is a MacBook Pro 2020 and has USB c ports only, would the Thunderbolt to USB C or Thunderbolt to HDMI converter attached to the above cable do the job?

Thanks

Boris

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Answer 8

borislav77 Author

Level 1

8 points

Jan 12, 2021 11:21 AM in response to barberlives123

Hi There,

Thanks for the reply, I did read this post and this is what prompted me to give this a try but it didn’t work, do you have any other suggestions I could try?

thanks

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Answer 9

borislav77 Author

Level 1

8 points

Jan 14, 2021 7:07 AM in response to Malcolm J. Rayfield

Hi Malcolm,

Just got the cable you suggested and it does not seem to work either, do you have any other suggestions?

Regards,

Boris

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