hey guys I'm currently in the market for a switch device that can allow me to hook my 2011 iMac up to the Apple 27" cinema display and also connect a Ps3/xbox up to the display as well but i haven't been successful . Help!!!
Atlona, Kanex and Belkin are a few names that make HDMI to mDP adapters...not sure how those work on the latest model of the ACD (if that's what you have). Those adapters will not work with your thunderbolt iMac unfortunately, there is no way to do it...yet. Everyone claims to be working on it but it just depends on how long it takes for the devices to be developed.
You need more than a cable. The 2009/2010 iMacs support input from Displayport Devices only. HDMI is supported with a more expensive adapter like those listed above in Post#2. I use a mini-displport to mini-displayport cable to connect my Alienware or MBP laptops to the iMac display. It works very well and supports full native resolution on the iMac display.
The Alienware has some audio glitches but the MBP (of course) works perfectly.