iMac 27” mid 2011 target display mode not working

I am tearing my hair out trying to get my old iMac (27" mid 2011, High Sierra 10.13.6) to use as an external monitor with target display mode on my old MacBook Pro (13" 2012, Catalina 10.15.7). I'm using thunderbolt 2 cable to connect them. I've followed all the steps here Use your iMac as a display with target display mode – Apple Support (AU) and nothing happened. iMac won't display MacBook Pro. I’m using the original keyboard that came with the iMac and Apple thunderbolt 2 cable. Can't figure out why. Need help!!!

iMac 27″, macOS 10.13

Posted on Oct 28, 2024 3:07 PM

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6x6

Level 6

15,470 points

Posted on Oct 30, 2024 6:32 AM

emmajunli wrote:

Thanks for the tip. Yup the target disk mode works. So we can rule out the possibility of a bad thunderbolt 2 cable connection. Too bad I’ve already ordered a new thunderbolt 2 cable… Plus the issue persists - iMac still won’t display MacBook Pro

I’m no hardware expert but I gather that a Thunderbolt cable carries 2 signals (besides power): data and video. There is still a chance that your current cable fails on the video signal (and not on the data signal) and that the replacement cable might work.

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17 replies

Oct 30, 2024 3:58 PM in response to Servant of Cats

Not disagreeing with you. 👍🏽

emmajunli Author

Level 1

4 points

Nov 12, 2024 3:38 AM in response to D.I. Johnson

Well guess what? The new cable makes no difference at all! Sigh…

iMac 27” mid 2011 target display mode not working