Abstract: A dynamic random access memory (RAM) addressing controller comprises a plurality of connectors connectible with a plurality of memory boards which use different addressing arrangements. A timing generator for generating a timing signal is provided for multiplexing address signals applied to a dynamic RAM storage. The controller also includes an input unit for applying an address signal of predetermined width, an address selector for mutliplexing a part of the address signal supplied from the input unit in accordance with the timing signal, a branching unit for supplying another part of the address signal of predetermined width from the input unit to a corresponding portion of each of the connectors respectively, and another branching unit for branching the address signal of the multiplexed part from the address selector in such a way as to be applied to a corresponding portion of each of the connectors. Memory boards carrying highly-integrated memory devices are replaceable in memory board slots.