A computer memory, having one or more of a semiconductor memory device having an internal memory array comprising a plurality of semiconductor dynamic random access memory (DRAM) cells arranged in a matrix of rows and columns, and provided as a memory module rank of such memory devices arranged in an array on a DIMM of one or more of said semiconductor memory device on a substrate which can be coupled via a memory device data interface to a memory system as a memory subsystem, each of said memory device having a low power shut-down state that can be activated using a common memory data interface. Control of power to a DRAM issues over the data interface two commands to a DRAM power control command decode, a power-state program signal and a power-state reset signal as a power-state control commands to control the power state of said DRAM, and to activate for READ/WRITE a memory cell as a normal active or spare device.