Abstract: An easily installable and easily expandable electromechanical memory assembly for a data processing system includes: a frame having a backplane, a plurality of printed circuit board connectors on the backplane, and conductors on the backplane which interconnect the connectors; a controller on a printed circuit board which is plugged into one of the connectors and consists essentially of logic circuitry for generating and receiving control signals on the backplane conductors; and multiple data storage units; each unit being mounted on a separate printed circuit board, plugged into a separate connector, and consisting essentially of a mechanical drive mechanism which reads data by physically moving a data storage medium past a data sensor in direct response to the control signals from the controller on the backplane conductors.