Memory systems and methods for improved power management

A method for providing access to a rank of memory devices on at least one memory module, the rank including a first sub-rank of memory devices and a second sub-rank of memory devices, the method comprising:

• receiving an enable command at the at least one memory module, the enable command accompanying chip-select information;
• powering the memory devices in the first and second sub-ranks of the memory devices responsive to the chip-select information;
• and
• asserting chip-select signals to the powered memory devices in the first and second sub-ranks of the memory devices responsive to the chip-select information.

A memory module comprising:

• a number of memory devices each having a memory-device enable terminal;
• a command port to receive commands from a controller component external to the memory module;
• and
• a decoder communicatively coupled to the command port and the memory-device enable terminals, the decoder to:
• receive a configuration value from the controller component specifying a fraction of the number of the memory devices;
• receive, as one of the commands, an enable command accompanying chip-select information;
• decode the chip-select information responsive to the configuration value specifying the fraction of the number of the memory devices, the decoding specifying a subset of the memory devices, the subset of the memory devices of the fraction of the number of the memory devices;
• and
• power the specified subset of the memory devices responsive to the decoded chip-select information.