Improving energy efficiency of embedded DRAM caches for high-end computing systems

The number of cores in a single chip in the nodes of highend computing systems is on rise, due, in part, to a number of constraints, such as power consumption. With this, the size of the last level cache (LLC) has also increased significantly. Since LLCs built with SRAM consume high leakage power, power consumption of LLCs is becoming a significant fraction of processor power consumption. To address this issue, researchers have used embedded DRAM (eDRAM) LLCs which consume low leakage power. However, eDRAM caches consume a significant amount of energy in the form of refresh energy. In this paper, we propose ESTEEM, an energy saving technique for embedded DRAM caches. ESTEEM uses dynamic cache reconfiguration to turn off a portion of the cache to save both leakage and refresh energy. It logically divides the cache sets into multiple modules and turns off possibly different number of ways in each module. Microarchitectural simulations confirm that ESTEEM is effective in improving performance and energy efficiency and provides better results compared to a recently-proposed eDRAM cache energy saving technique, namely Refrint. For single and dual-core simulations, the average energy saving in memory subsystem (LLC+main memory) with ESTEEM is 25.8% and 32.6% respectively, and the average weighted speedup is 1.09X and 1.22x respectively. Additional experiments confirm that ESTEEM works well for a wide-range of system and algorithm parameters.