One thing mentioned is that the cache die is now the same size as the CCD, when previously it was notably smaller and "dummy silicon" used to fill in the gap an

One thing mentioned is that the cache die is now the same size as the CCD, when previously it was notably smaller and "dummy silicon" used to fill in the gap and get everything to the same height. I can see "stacking" larger dies on top of smaller being extremely difficult to align. Perhaps the trade off was made to allow a smaller cache die (so lower cost) at the cost of requiring it to be "on top".