Improving VLIW Processor Performance Using Three-Dimensional (3D) DRAM Stacking

This work studies the potential of using emerging 3D integration to improve embedded VLIW computing system. We focus on the 3D integration of one VLIW processor die with multiple high-capacity DRAM dies. Our proposed memory architecture employs 3D stacking technology to bond one die containing several processing clusters to multiple DRAM dies for a primary memory. The 3D technology also enables wide low-latency buses between clusters and memory and enable the latency of 3D DRAM L2 cache comparable to 2D SRAM L2 cache. These enable it to replace the 2D SRAM L2 cache with 3D DRAM L2 cache. The die area for 2D SRAM L2 cache can be re-allocated to additional clusters that can improve the performance of the system. From the simulation results, we find 3D stacking DRAM main memory can improve the system performance by 10%~80% than 2D off-chip DRAM main memory depending on different benchmarks. Also, for a similar logic die area, a four clusters system with 3D DRAM L2 cache and 3D DRAM main memory outperforms a two clusters system with 2D SRAM L2 cache and 3D DRAM main memory by about 10%.