A memory structure is described. In one embodiment, the memory structure comprises a memory controller configured to receive a clock signal and to be coupled to a plurality of memory modules via a single address/control bus. The memory controller couples to each of the plurality of memory modules via a separate chip select signal for each memory module. The memory controller issues commands across the address/control bus to the memory modules in an interleaved fashion in accordance with the timing supplied by the clock. During a waiting period after issuance of a command to one memory module, the memory controller can issue commands to a different memory module.