US Patent 7676639 Separate handling of read and write of read-modify-write

Separate handling of read and write operations of Read-Modify-Write Commands in an XDR™ memory system is provided. This invention allows the system to issue other commands between the reads and writes of a RMW. This insures that the dataflow time from read to write is not a penalty. A RMW buffer is used to store the read data and a write buffer is used to store the write data. A MUX is used to merge the read data and the write data, and transmit the merged data to the target DRAM via the XIO. The RMW buffer can also be used for scrubbing commands.