Better silicon. For example the main difference between the 290 and 290x is silicon. Better silicon will have more units enabled and could handle higher clock s

Better silicon. For example the main difference between the 290 and 290x is silicon. Better silicon will have more units enabled and could handle higher clock speeds. (Others are likely to be dead or dodgy). Although at 450 Watts I doubt there will be much in the way of high clock speed. When it comes to workstation graphics Nvidia drivers behave differently when using a Quadro. (Eg: duel monitor support in Linux)