Patent ID: 7921271

Claim:
A hub module for a memory subsystem of a computer system, 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 transmitting memory access commands including write data to at least one cluster module and receiving read data from multiple memory modules of a cluster of multiple memory modules, said cluster module being a memory module of said cluster, each memory module of said cluster storing data at addressable storage locations, 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, the respective point-to-point communications link operating at a second bus frequency less than said first bus frequency, read data stored in the corresponding memory module of said multiple memory modules of said cluster, 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 including write data from said hub directly to at least one respective said cluster module, each said cluster module being a memory module of said multiple memory modules of said cluster, each said cluster module having a third interface for forwarding memory access commands including write data received from said hub to a respective plurality of said multiple memory modules of said cluster, at least some said memory access commands including write data, at least some 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.