Cast your minds back to the launch of the 27" iMac in mid-2009. One of the new features was Target Display Mode, which introduced the ability to use the iMac as a pure external monitor, bypassing the built-in computer entirely. This could be useful if you wanted to dock a laptop to a big screen temporarily -- or if you were worried that the substantial investment in a 27" screen would, in years to come, be hobbled by the ageing CPU and GPU inside the iMac. The theory was that you could eventually just stop using everything but the display.
However, Apple has quietly dropped the feature on the latest iMacs, which were announced today
