hd 4000 wafer? What are you talking about? The wafer's size affects the yields, not how big the card will be. The die size won't really make much of a difference either since they can only get so big before they're too expensive to produce. The thing that makes the biggest difference is how complex the pcb is (for instance, that of the original r600 was extremely complex due to the 512bit memory and thus was very large) which also includes the power supply and the amount of memory on board.