I'm going to look genuinely stupid now... but oh well.
Why is bandwidth so important given the relatively small size of the ESRAM? Surely you'd be limited by the size of the memory before you'd be limited by your ability to ship data to / from it.
Not necessarily with ROPs, where you have a lot of bandwidth consumption mapping to relatively small areas of memory. Well, we thought that ROPs in Durango would be relatively unconstrained by bandwidth as they were in Xenos (256GB/s). And that this would give it the same relative advantages and allow it to excel in some cases, where you were bound by buffer bandwidth or buffer processing.
But now it looks like you have 170GB/s of bandwidth to use, where 102GB/s is shuffling to and from 32MB and 65GB/s to the rest.
It is 'worse' than I thought before...before I saw strengths and weaknesses vs Orbis, now I see weakness and added complexity for the sake of main memory capacity.