US Patent 7117316 Memory hub and access method having internal row caching

A computer system includes a controller coupled to a plurality of memory modules each of which includes a memory hub and a plurality of memory devices. The memory hub includes a row cache memory that stores data as they are read from the memory devices. When the memory module is not being accessed by the controller, a sequencer in the memory module generates requests to read data from a row of memory cells. The data read responsive to the generated read requests are also stored in the row cache memory. As a result, read data in the row being accessed may be stored in the row cache memory even though the data was not previously read from the memory device responsive to a memory request from the controller.