Die stacking and chip stacking

Today I saw a slashdot posting for a tear down of the iPhone. Besides being very interesting in general one thing struck me, and that was the main processor. Not only was this thought to be an ARM11 part, but it seems to have a 256 MB of SDRAM stacked in the same package. This reminds me of a tear down I saw for the Nokia 7280. This is a very similar idea except this time the memory stack is a separate chip from the processor. I have the paper copy of this article, and the picture shows the memory stack chip soldered directly on top of the processor. The memory stack in the 7280 is also from Samsung, but it includes 3 types of memory: NAND flash, NOR flash and SDRAM. Vertically stacking dies has become very important to reducing board area. I especially like the way the stack on the 7200 works because then the package for the processor can stay the same, but incremental advances in the memory stack can be made.