Exploring main memory design based on racetrack memory technology

Emerging non-volatile memories (NVMs), which include PC-RAM and STT-RAM, have been proposed to replace DRAM, mainly because they have better scalability and lower standby power. However, previous research has demonstrated that these NVMs cannot completely replace DRAM due to either lifetime/performance (PCRAM) or density (STT-RAM) issues. Recently, a new type of emerging NVM, called Racetrack Memory (RM), has attracted more and more attention of memory researchers because it has ultra-high density and fast access speed without the write cycle issue. However, there lacks research on how to leverage RM for main memory. To this end, we explore main memory design based on RM technology in both circuit and architecture levels. In the circuit level, we propose the structure of the RM based main memory and investigate different design parameters. In the architecture level, we design a simple and efficient shift-sense address mapping policy to reduce 95% shift operations for performance improvement and power saving. At the same time, we analyze the efficiency of existing optimization strategies for NVM main memory. Our experiments show that RM can outperform DRAM for main memory, in respect of density, performance, and energy efficiency.