Performance Analysis of Spin Orbit Torque Magneto-Resistive RAM Caches in 4-core ARM Systems

Spin Orbit Torque Magnetic Random Access Memory (SOT-)MRAM is gaining interest as it eradicates several limitations posed by its predecessor Spin Transfer Torque (STT-)MRAM, yet inherits all its advantages. This work explores in detail, the suitability of SOT-MRAM implemented caches in different levels of memory hierarchy in comparison to conventional SRAM technology, over several performance parameters like area, energy consumption and execution time for an embedded benchmark suite. Our circuit-level analysis shows that SOT-MRAM outperforms SRAM for caches (>128 KB), and only lags in area and read-access energy for smaller caches. A typical 512 KB SOT-MRAM cache improves area by 1%, read/write latency by 33/38%, and leakage by over 99% than that of SRAM memory technology. The architecture-level analysis confirms that on average SOT-MRAM is energy efficient by 74% in L1, 97.2% in L2 and 89.3% in both (i.e., L1 + L2) implementations against SRAM, for a 22nm technology node. We also estimate that SOT-MRAM only solution offers similar to 68.8% energy savings and similar to 79.5% better EDP than Hybrid (L1-SRAM and L2-SOT) memory hierarchy for multi-core ARM processors.