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BeanConnoisseur

macrumors newbie
Original poster
Aug 31, 2020
3
0
Hi!
I'm currently running High Sierra on a 27" iMac (Late 2009). I use this iMac as an external monitor fairly frequently with a Mini DisplayPort cable, and I'm hoping to upgrade to Catalina (unsupported officially) using the Catalina Patch for unsupported devices.

I've seen mixed results posted about this, so I wanted to ask here -- has anyone gotten Target Display mode / external monitor mode working successfully with an iMac (2009) using Mini DisplayPort and Patched Catalina? I've heard that Thunderbolt 2 works on Catalina on 2011-2012 devices, but what about Mini DisplayPort with iMacs from 2009?

Sorry for any confusion in terms, this is my first post here and I'm hoping to learn whether I'll be able to use this or not :)
 
Last edited:

Nguyen Duc Hieu

macrumors 68030
Jul 5, 2020
2,559
800
Ho Chi Minh City, Vietnam
Hi!
I'm currently running High Sierra on a 27" iMac (Late 2009). I use this iMac as an external monitor fairly frequently with a Mini DisplayPort cable, and I'm hoping to upgrade to Catalina (unsupported officially) using the Catalina Patch for unsupported devices.

I've seen mixed results posted about this, so I wanted to ask here -- has anyone gotten Target Display mode / external monitor mode working successfully with an iMac (2009) using Mini DisplayPort and Patched Catalina? I've heard that Thunderbolt 2 works on Catalina on 2011-2012 devices, but what about Mini DisplayPort with iMacs from 2009?

Sorry for any confusion in terms, this is my first post here and I'm hoping to learn whether I'll be able to use this or not :)

The official answer will be NO.
Target display mode on old iMac models is only supported up to High Sierra.

 

Juicy Box

macrumors 604
Sep 23, 2014
7,339
8,552
The official answer will be NO.
Target display mode on old iMac models is only supported up to High Sierra.

I am not sure if that is accurate. I know it is on the official Apple support page, but Apple has stopped updating the Target Display Mode page and has since archived it.

While I have not done it myself yet, there has been many reports of Target Display Mode working with the target iMac on both Mojave and Catalina.


Hi!
I'm currently running High Sierra on a 27" iMac (Late 2009). I use this iMac as an external monitor fairly frequently with a Mini DisplayPort cable, and I'm hoping to upgrade to Catalina (unsupported officially) using the Catalina Patch for unsupported devices.

I've seen mixed results posted about this, so I wanted to ask here -- has anyone gotten Target Display mode / external monitor mode working successfully with an iMac (2009) using Mini DisplayPort and Patched Catalina? I've heard that Thunderbolt 2 works on Catalina on 2011-2012 devices, but what about Mini DisplayPort with iMacs from 2009?

Sorry for any confusion in terms, this is my first post here and I'm hoping to learn whether I'll be able to use this or not :)
I am pretty sure you can, but what will be the source?

You may have to use a different adapter depending on the source.
 

Nguyen Duc Hieu

macrumors 68030
Jul 5, 2020
2,559
800
Ho Chi Minh City, Vietnam
I am not sure if that is accurate. I know it is on the official Apple support page, but Apple has stopped updating the Target Display Mode page and has since archived it.

While I have not done it myself yet, there has been many reports of Target Display Mode working with the target iMac on both Mojave and Catalina.

I am pretty sure you can, but what will be the source?

You may have to use a different adapter depending on the source.

I totally agree with you. And I really hope that Target display mode still remain workable in newer Mac OS version.
For video signal, the mechanism of it is just the machine receives a command by a combination of keys pressed to reroute the input signal from mini-display port to the eDP port (on the logic board).
The problems here are:
- Whether the new OS version maintains support to that command or not?
- Whether the patch impacts (nullify) that command or not?
- In case Apple intentionally disable that command, does the patch re-enable that command?
 

Juicy Box

macrumors 604
Sep 23, 2014
7,339
8,552
- Whether the new OS version maintains support to that command or not?
- Whether the patch impacts (nullify) that command or not?
It appears this is an existing issue, one patch might break it, another fixes it again.

It is technically no longer supported, but Apple I guess is still trying to support it unofficially.

I bet there might be a patch or maybe Big Sur that just permanently breaks it. But, hopefully just breaks it for the target computer, letting the user keep it on an older OS just to use as a Display, and not breaking it for the source Macs.

So, my advice for anyone that is using an old iMac for Target Display Mode is to keep a bootable back up of an OS that you know Target Display Mode works with.
 

pappkristof

macrumors member
Aug 1, 2015
94
100
Hi!
I'm currently running High Sierra on a 27" iMac (Late 2009). I use this iMac as an external monitor fairly frequently with a Mini DisplayPort cable, and I'm hoping to upgrade to Catalina (unsupported officially) using the Catalina Patch for unsupported devices.

I've seen mixed results posted about this, so I wanted to ask here -- has anyone gotten Target Display mode / external monitor mode working successfully with an iMac (2009) using Mini DisplayPort and Patched Catalina? I've heard that Thunderbolt 2 works on Catalina on 2011-2012 devices, but what about Mini DisplayPort with iMacs from 2009?

Sorry for any confusion in terms, this is my first post here and I'm hoping to learn whether I'll be able to use this or not :)
Hi!
Did you try it? Does Target Display Mode work on an 2009 iMac with Catalina (or Big Sur)?
 
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