POP history

We were very enthused with the original POP concept for the first
Beagleboard, which had CPU, SDRAM and NAND Flash stacked. Then, the
Beagleboard Xm came out with just CPU and SDRAM. Finally, we have the
BeagleBone, which does not appear to have anything stacked. Was the
gradual change due to manufacturing problems or something else?

POP is very popular and very easy to manufacture and the decision not to use it here had nothing to do with manufacturing concerns of any kind whatsoever. BeagleBone has no POP because the processor did not come in a POP capable package. That was a product decision by TI based on use of DDR2 devices which it supports which do not come in POP. POP is mainly mobile DDR type memories.

From a BeagleBone aspect, we can only use the technology available to us. We do not make the chips.