Target Display Mode Compatible 1.8m (6ft) Mini DisplayPort Cable Male to Male
Works with any Mac or PC with a Mini DisplayPort
This NewerTech cable will allow you to pass through audio and video from your Mini DisplayPort equipped Mac to a 27" Apple iMac to make use of its large screen and audio system. Additionally, you can use this high quality cable to connect a Mini DisplayPort equipped Mac or PC to a display/monitor with an available Mini DisplayPort input connection.
Maximum Resolution: 2560 x 1600
Target display mode is a function supported by 27" 2009 and 2010 iMacs, where you can connect other Mini DisplayPort devices (MacBook, MacBook Pro, MacBook Air, iMac, Mac Mini and Mac Pro) to the iMac and utilise it as a monitor. Mini DisplayPort machines (anything released before 2011) do not support Thunderbolt cables, so a standard Mini DisplayPort cable (male to male) is required. (Thunderbolt iMacs do support target display mode, but only between other thunderbolt enabled machines)
See this help page for details and machine compatibility Click Here