1. A method comprising: detecting a memory command directed to a logical rank; detecting a number of physical ranks mapped to the logical rank from a plurality of physical ranks; determining whether the memory command is to be issued to the number of physical ranks; and issuing the memory command to the number of physical ranks based on a determination that the memory command is to be issued to the number of physical ranks, wherein issuing the memory command includes using a look-up table with the logical rank and a portion of a logical row address of the logical rank to identify each of the physical ranks mapped to the logical rank and a corresponding sub-channel for transmitting physical-memory-element values between a memory controller and said each of the physical ranks mapped to the logical rank, the corresponding sub-channel being selected from a plurality of sub-channels that transmit data between the memory controller and the physical ranks, the corresponding sub-channel being configured to transmit data between the memory controller and said each of the physical ranks mapped to the logical rank by enabling data transmission in the corresponding sub-channel in response to the identification of the corresponding sub-channel, and the physical-memory-element values being stored at one or more memory locations of said each of the physical ranks mapped to the logical ranks.