A Study On Novel Hybrid Main Memory For High Performance And Low Power

In the computer architecture,the traditional DRAM main memory suffered serious power consumption,performance,capacity and data reliability and other issues.The emergence of new storage technology and materials are hopeful for finding memory that can replace DRAM.Among the novel memory technologies,phase change memory(PCM)has many advantages such as higher storage density,lower idle power consumption and nonvolatile.However,there is a big gap between the novel nonvolatile memory and DRAM in R/W speed,R/W power consumption and endurance.Using PCM instead of DRAM as a single main memory does not work well.Therefore,the hybrid main memory architecture based on DRAM and PCM came into being,which can combine the advantages of both to achieve better system power and performance.At present,the existing hybrid main memory research is based on the PCM as the leading.However,there are still some shortcomings in these studies,such as the high cost of highcapacity PCM,greater hardware overhead and higher complexity.Reasonable and effective hybrid architecture main memory can combine the advantages of two kinds of memory,while overcoming traditional DRAM memory problems.Therefore,this thesis focuses on the challenges of traditional DRAM and uses hybrid architecture to study and optimize it.In order to evaluate the power consumption and performance of the hybrid architecture,a joint simulation platform based on Gem5 and DRAMSim2 simulator is built on the basis of analyzing the mainstream architecture simulator.Firstly,to address the problem of refresh power consumption in traditional DRAM,this thesis proposes a Refresh-Released Hybrid Memory(RRHM)hybrid main memory.By properly dividing and assigning hot and cold pages in different areas,the no refresh area in the DRAM and the PCM does not need refresh.So the refresh operation and system power consumption can be effectively reduced.The simulation results show that the total power consumption in the RRHM is reduced by an average of 28.5%,with the refresh power consumption reduced by 71.9%.Then,in order to meet the application demand of load change in sever,this thesis proposes a Power Mode Switch(PMS)hybrid architecture main memory solution.By detecting the memory footprint and the frequency of access,the memory system can adaptive switch between different power modes.The mode switching process is done in the background,so it does not affect system performance.The simulation results show that the total power consumption in the PMS is reduced by an average of 30.2% with the static power consumption reduced by 38.2%.Finally,to face the error problem caused by VRT/data dependent in multi-rate refresh scheme,this thesis proposes a Weak/Error Row Remap(WERR)hybrid architecture main memory solution.By remapping the weak/error row of DRAM into PCM,it can effectively deal with the data error caused by VRT/data dependent and can reduce the refresh rate of DRAM,so as to reduce the power consumption.The simulation results show that the total power consumption in the WERR is reduced by an average of 20.3% with the refresh power consumption reduced by 61.6%.