A three-dimensional stacked (3DS) memory module includes multiple memory chips and a data I/O chip physically integrated into the 3D stack. The data I/O chip includes multiple data interfaces and multiple respectively corresponding data buffers. A memory controller routes data traffic through all available data interfaces for maximum bandwidth. In some circumstances, the memory controller directs the data I/O chip to shut down (de-activate) one or more of the data interfaces (for example, to reduce power consumption of the memory module). All subsequent data traffic to and from the memory module is routed through the remaining active interfaces. All physical addresses in the 3DS memory module are addressable through the remaining active interfaces. In some circumstances, the memory controller directs the data I/O chip to re-activate some or all of the de-activated data interfaces. Once re-activated, subsequent data traffic to and from the memory module can again be routed through all active interfaces.