STFL-DDR: Improving the Energy-Efficiency of Memory Interface

Power dissipation is a significant problem limiting the performance of today's computer systems. One of the main contributors to power consumption in microprocessors is data movement in cache and memory interface. Several solutions such as low power interconnects, energy-aware data encoding, and low power signaling have been proposed to mitigate this problem. Almost all of these techniques result in a significant system performance degradation. This article examines the application of a novel technique, called STFL-DDR, for hybrid signaling on low-power DRAM interface. To keep the power consumption low, STFL-DDR employs a high-performance clock rate for transferring data on low power wires. To avoid any signal deterioration, STFL-DDR employs data encoding/decoding to prevent each wire from switching in any two consecutive cycles. STFL-DDR creates new opportunities for optimizing the energy-efficiency of DRAM systems. We compare the efficiency of STFL-DDR with the state-of-the-art methods by simulating a mix of 12 parallel benchmark applications on a muticore system. Our simulation results indicate that STFL can reduce the energy consumption of a contemporary DRAM interface by 17 percent as compared to an LPDDR baseline while achieving the throughput of a high-performance DRAM. Applying STFL to both last level cache and DRAM interface results in improving the system energy, energy-delay product, and performance by 8, 15, and 9 percent respectively. Compared with a high-performance memory interface, STFL improves the system energy and energy-delay product by 25 and 75 percent, while reaching 98 percent of the average performance of the high-performance system.