A memory module such as a DIMM includes two separate memories with corresponding data, address and control interfaces. Each separate memory core includes plural memory banks for corresponding portions of the data interface. The separate interfaces include separate byte strobes and control signals. The two memories may be separately powered or share power connection. The two memories may be disposed on a single semiconductor integrated circuit or separate semiconductor integrated circuit. The two memories may be connected to two external memory interfaces of a single data processor or to separate data processors.