was the assumption for the 4870 to go with 1+3, and they did 1+4?

theres really only 2 things to look at
perf per watt = efficiency
perf per mm2 = costs

it seems that only 1 of those is really changing by much. which isnt bad considering its on the same process and we cant really expect too much with perf/watt (unless its like nvidia where they chopped off the server stuff to shave power for the gf104)