Exploring DRAM Last Level Cache for 3D Network-on-Chip Architecture

Abstract

In this paper, we implement and analyze different Network-on-Chip (NoC) designs with Static Random Access Memory (SRAM) Last Level Cache (LLC) and Dynamic Random Access Memory (DRAM) LLC. Different 2D/3D NoCs with SRAM/DRAM are modeled based on state-of-the-art chips. The impact of integrating DRAM cache into a NoC platform is discussed. We explore the advantages and disadvantages of DRAM cache for NoC in terms of access latency, cache size, area and power consumption. We present benchmark results using a cycle accurate full system simulator based on realistic workloads. Experiments show that under different workloads, the average cache hit latencies in two DRAM based designs are increased by 12.53% (2D) and reduced by 27.97% (3D) respectively compared with the SRAM. It is also shown that the power consumption is a tradeoff consideration in improving the cache hit latency of DRAM LLC. Overall, the power consumption of 3D NoC design with DRAM LLC has reduced 25.78% compared with the SRAM design. Our analysis and experimental results provide a guideline to design efficient 3D NoCs with DRAM LLC.