The mid 2010 and later unibody MacBook (7,1) supports it.
Late 2009 or later iMacs also support it. Mid 2010 or later MacBook Pros support audio through the port. Those that can't will need to have auxiliary speakers connected to the 3.5mm audio jack or other solution through a separate cable system. Only certain Macs can output audio through the mini display port. It is important to know which computers support audio through the port. It seems some adapters may or may not support audio.
