AT-DP200 with Thunderbolt Display
Found these on the manufacturer's web site:


  Note2: The DP400 requires Dual Link video card which support 2560x1440 in order to output 2560x1440 to a display. Please make sure you card is Dual Link.
  
  Note3: The AT-DP400 will not support 2011 iMac 27-inch with
  Thunderbolt connection, Atlona is working on a new product which will.