Use a 27″ iMac as an External Display for Another Mac
One of the coolest features of the 27″ iMac is it’s beautiful LED screen with a whopping 2560×1440 resolution, but what’s even cooler is the ability to use that gorgeous display as an external display for another Mac. So if you want to use an iMac as an external screen for another Mac, you’ll need to use a featured called Target Display Mode and select the 27″ iMac as the video input. That may sound complicated but it’s really pretty easy, let’s walk through this:
What you need to use the 27″ iMac as an external monitor for another Mac
Once you have the hardware, just plug the Mini DisplayPort to Mini DisplayPort cable from the source machine into the iMac and the iMac should automatically enter into Target Display Mode and show video from the source machine. If for whatever reason that doesn’t work, hit Command + F2 to enter in and out of Target Display Mode on the 27″ iMac.
As far as I know this only works on the 27″ iMac, I don’t think the smaller screened iMac’s have this ability in their current revisions. Let us know if you get this feature working on the 22″ iMac or another model.
The CultOfMac has an interesting solution that involves daisy-chaining together standard Mini DIsplayPort to DVI cables to get the same effect, but it’s a lot better to just get the proper cable since they aren’t too expensive.
Courtesy of CultOfMac, the below video demonstrates an iMac being used as an external display for a MacBook Pro, it shows the basic setup and how fast it is, it may be useful you’re having any troubles getting this great feature to work.
For more information check out Apple’s Knowledge Base article on the topic.