Achieve 10X DRAM Bandwidth Improvement with a DDR Controller Read Reorder Buffer

Achieve 10X DRAM Bandwidth Improvement with a DDR Controller Read Reorder Buffer

The read reorder buffer (RRB) is a silicon-proven architectural enhancement available in Synopsys uMCTL and uMCTL2 DDR memory controller IP products. This white paper will explain the concept of the read reorder buffer and explain how a read reorder buffer can improve memory bandwidth. It then concludes with experimental results showing how DRAM controllers with different architectures can achieve vastly different DRAM bus utilizations of 10%, 66%, or 100% from the same input traffic stream, depending on whether the architecture has no RRB, an RRB with external scheduling, or an RRB with content-addressable memory (CAM)-based scheduling.

Table of Contents

  1. Introduction 
  2. Reordering transaction in a DRAM controller
    1. Restriction on transaction reordering
    2. Write reordering and read/write reordering
  3. Experimental setup
    1. Experimental results
    2. Potential concerns
  4. Conclusion

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