In addition, DDR4 has been designed in such a way that stacked memory devices may prove to be a key factor during the lifetime of the technology, with stacks of up to 8 memory devices presenting only a single signal load.

ENGADGET: JEDEC announces final DDR4 RAM specification

Flash memory has played an important role in these mobile consumer devices because it is rugged, flash memory chips can be stacked to enable compact devices, it uses small amounts of battery power and enough storage capacity can be included to make these devices useful for some common tasks such as email and media playing.

FORBES: Changing Digital Storage Requirements for Clouds and Mobile Devices