Comment Re:Every Two Years (Score 2) 79
Stacking chips is not the same as a monolithic chip with multiple active layers. When chips are stacked, each chip can be tested before stacking, and the final yield becomes a question of successful interconnect and not damaging chips during assembly. With multilayer chups each layer must be perfect for the device to work.
I'd guess that they're not using a process with the smallest geometry. That way they can have a process that is basically very high yield for each layer; the resulting die will have acceptable yield.
An advantage of monolithic multilayer over stacking is that there's no risk that the thermal flow will have gaps.