Model A1312 / Mid 2010 / 3.2 GHz Core i3 or 2.8 & 3.6 GHz Core i5 or 2.93 GHz Core i7, ID iMac11,3

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Target Display Mode not working. Is thunderbolt the problem?

I'm trying to use an old iMac 27-inch (Mid 2010) as a monitor, using the Target Display Mode without success. I'm connecting a MacBook Pro (Retina, 15-inch, Mid 2015).

The cable is a completely new Thunderbolt - Thunderbolt cable. I've tried resetting SMC and NVRAM on the iMac which haven't solved the problem. I've also tried the VirtualKVM application but it looks as if the Thunderbolt port isn't recognising the cable.

Obviously the CMD+F2 option isn't working either.

Any ideas?

Answer this question I have this problem too

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You'll need to get a DisplayPort cable Vs a Thunderbolt cable. Surprising even though they look the same they don't work the same!

Your iMac has a mini DisplayPort not Thunderbolt so it can't power the cable which is needed for the head-end circuitry located in the cables connector.

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Hi Dan, yeah so I've just figured this out. Do you know if it specifically MUST be a mini to mini? Right now I'm using a mini to hdmi, still no luck :(


Thats the only way I've used it between two Mac's (DP to DP).

Here's a bit more on how to use it: The Ins and Outs of Your iMac’s Target Display Mode and here's Apple's T/N on it: Use your iMac as a display with Target Display Mode


Hi Jacob, i've faced exactly same problem, solved with a dp mini to dp mini cable. i have tried thunderbolt too. not worked but dpmini dpmini cable works like a charm. Immediately works after connect them together.


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Dan's answer is correct, they can work together only with DP Mini to DP Mini cable. I have tried both thunderbolt and DP Mini and only DP Mini worked.

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jacob will be eternally grateful.
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