How to use a late 2009 27" iMac as a display for a 2020 Macbook Pro?

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Level 1

4 points

How to use a late 2009 27" iMac as a display for a 2020 Macbook Pro?

I found this thread: https://discussions.apple.com/thread/8024535

It says my late 2009 27" iMac can be used as a second display for my 2020 Macbook Pro. It instructs me to use a Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter and a Thunderbolt or a Mini DisplayPort to Mini DisplayPort cable.

I purchased the adapter and Mini DisplayPort cable and this configuration does not work. ON the box of the adapter in fine print it shows Mini DisplayPort in red with an X saying it is not compatible. That must be why it did not work for me.

So, apparently the adapter requires a Thunderbolt cable. However, I read on the Apple website that any Mac older than 2011 in not Thunderbolt compatible. So, does that mean I'm out of options? or Will the Thunderbolt cable work to activate the Mini DisplayPort?

Posted on Sep 10, 2020 1:24 PM

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Answer 1

Allan Jones

Level 9

72,302 points

Sep 10, 2020 2:31 PM in response to barrydollar

That thread is from 2017 and has out of date information. 2020 Macs cannot take advantage of Target Display Mode. Please see Apple's now-archived help document on TDM:

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

especially noting this part:

One person has posted that he was able to make TDM work from a 2020 MacBook Pro to a 2009-2010 iMac 27, but others responding said they have not been able to make it work last time I saw the thread.. Sorry, I don't have a link to that thread but you can try searching, It was in the Using iMac forum within the last month.

Success reports I've seen on TDM using newer supported iMacs as the monitor for 2019 and older thunderbolt-3 Macs say the T3 cable need to connect to T3 computer and any adapters go on the iMac's end.

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Answer 2

rkaufmann87

Level 10

143,952 points

Sep 10, 2020 2:41 PM in response to barrydollar

barrydollar,

The advice Allan provided is correct, it simply will not work. If your MBP needs an external display, please buy one. The good news is they have come way down in price. Hundreds have come before you and all have the same results, it simply does not work.

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Answer 3

barrydollar Author

Level 1

4 points

Sep 10, 2020 1:27 PM in response to barrydollar

ON this page regarding the adapter: https://support.apple.com/en-us/HT207266

"This adapter is not compatible with displays that use DisplayPort or Mini DisplayPort, such as the Apple LED Cinema Display. Thunderbolt and Thunderbolt 2 are not the same as Mini DisplayPort , though the ports have the same shape."

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Answer 4

Zahilla

Level 2

263 points

Sep 10, 2020 3:42 PM in response to barrydollar

Please look this info up before asking here. It WILL work as I’ve literally done it. The imac 2009 27 has Mini DisplayPort and doesn’t have the not working on 2020 macs restriction like 2011-2014 imacs do. If it was a thunderbolt mac it wouldn’t work but the 2009 is displayport so it will work and all you need is a Mini DisplayPort to thunderbolt 3 adaptor. Not a thunderbolt 3 to thunderbolt 2 adaptor.

https://www.amazon.com/DisplayPort-Adapter-QCEs-Thunderbolt-ChromeBook/dp/B073CVK6P6/ref=asc_df_B073CVK6P6/?tag=hyprod-20&linkCode=df0&hvadid=416771199824&hvpos=&hvnetw=g&hvrand=14010193066342453687&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9008133&hvtargid=pla-896805466979&psc=1&tag=&ref=&adgrpid=96633969569&hvpone=&hvptwo=&hvadid=416771199824&hvpos=&hvnetw=g&hvrand=14010193066342453687&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9008133&hvtargid=pla-896805466979

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Answer 5

Zahilla

Level 2

263 points

Sep 10, 2020 3:47 PM in response to rkaufmann87

Please please fact-check your information before replying, that is not correct. The 2009 27’ has Mini DisplayPort and doesn’t have the same restriction 2011-2014 target imacs do that have thunderbolt, 2009s and 2010s will even run with PCs. I’ve checked myself my 27 2009 works with a 2020 and another user on here tried a 2010 which worked for them

it seems target thunderbolt imacs no longer work in target display mode for 2020 macs but 2009-2010 do as they have Mini DisplayPort

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Answer 6

barrydollar Author

Level 1

4 points

Sep 14, 2020 5:40 AM in response to Zahilla

Here is the answer and solution for a 2020 Macbook Pro using target display mode on an older iMac, in my case a late 2009 27". My first attempt was the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter with a Mini DisplayPort to Mini DisplayPort cable. This did not work. Finally, I purchased a USB-C to Mini DisplayPort adapter on Amazon, used it with the Mini DisplayPort to Mini DisplayPort cable, and it worked perfectly. I plugged it into the laptop, then plugged it into the iMac, and the iMac automatically switched to the laptop's desktop.

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