Evaluation of Hybrid Memory Technologies Using SOT-MRAM for On-Chip Cache Hierarchy

Magnetic Random Access Memory (MRAM) is a very promising emerging memory technology because of its various advantages such as nonvolatility, high density and scalability. In particular, Spin Orbit Torque (SOT) MRAM is gaining interest as it comes along with all the benefits of its predecessor Spin Transfer Torque (STT) MRAM, but is supposed to eliminate some of its shortcomings. Especially the split of read and write paths in SOT-MRAM promises faster access times and lower energy consumption compared to STT-MRAM. In this paper, we provide a very detailed analysis of SOT-MRAM at both the circuit- and architecture-level. We present a detailed evaluation of performance and energy related parameters and compare the novel SOT-MRAM with several other memory technologies. Our architecture-level analysis shows that a hybrid-combination of SRAM for the L1-Data-cache, SOT-MRAM for the L1-Instruction-cache and L2-cache can reduce the energy consumption by 60% while the performance increases by 1% compared to an SRAM-only configuration. Moreover, the retention failure probability of SOT-MRAM is smaller than the probability of radiation-induced Soft Errors in SRAM, for a 65nm technology node. All of these advantages together make SOT-MRAM a viable choice for microprocessor caches.