Patent ID: 7996641

Claim:
A non-transitory machine readable medium embodying a design structure for a hub module for a memory subsystem of a computer system, the design structure comprising: a first interface for communicating with a memory controller over a first communications medium, said hub receiving memory access commands issued by said memory controller in said first interface, said first communications medium transferring data at a first bus frequency and requiring N cycles to communicate a unit of data accessed by a memory access command of said memory access commands, where N is greater than one; a second interface for communicating with a cluster of multiple memory modules storing data at addressable data storage locations over a second communications medium, at least some of said memory access commands issued by said memory controller accessing data in said cluster, said second interface comprising: (a) a plurality of read interfaces, each memory module of said cluster of multiple memory modules corresponding to a different respective read interface of said plurality of read interfaces, each read interface for receiving, on a respective point-to-point communications link connecting the corresponding memory module of said cluster of multiple memory modules directly to the respective read interface, read data stored in the corresponding memory module of said multiple memory modules of said cluster, the respective point-to-point communications link operating at a second bus frequency less than said first bus frequency, each memory module of said cluster storing a respective portion of each unit of data accessed by a respective memory access command of said at least some of said memory access commands issued by said memory controller accessing data in said cluster, and (b) at least one command interface separate from said plurality of read interfaces, each command interface of said at least one command interface for transmitting, on a corresponding unidirectional command link, memory access commands from said hub directly to at least one respective memory module of a subset of said multiple memory modules of said cluster, said subset of said multiple memory modules of said cluster containing fewer than all of said multiple memory modules of said cluster, at least one memory module of said subset of said multiple memory modules of said cluster forwarding memory access commands received from said hub to at least one of said multiple memory modules of said cluster which is not contained in said subset of said multiple memory modules of said cluster, said memory access commands including read commands, each read command transmitted on said at least one command interface containing a respective common address, wherein each memory module which receives a said read command transmits data stored therein at the corresponding common address directly to said hub on the corresponding point-to-point communications link.