Power management of hybrid DRAM/PRAM-based main memory

Hybrid main memory consisting of DRAM and non-volatile memory is attractive since the non-volatile memory can give the advantage of low standby power while DRAM provides high performance and better active power. In this work, we address the power management of such a hybrid main memory consisting of DRAM and phase-change RAM (PRAM). In order to reduce DRAM refresh energy which occupies a significant portion of total memory energy, we present a runtime-adaptive method of DRAM decay. In addition, we present two methods, DRAM bypass and dirty data keeping, for further reduction in refresh energy and memory access latency, respectively. The experiments show that by reducing DRAM refreshes, we can obtain 23.5%~94.7% reduction in the energy consumption with negligible performance overhead compared with the conventional DRAM-only main memory.