Mixed size crossbar based RRAM CNN accelerator with overlapped mapping method

Convolutional Neural Networks (CNNs) play a vital role in machine learning. CNNs are typically both computing and memory intensive. Emerging resistive random-access memories (RRAMs) and RRAM crossbars have demonstrated great potentials in boosting the performance and energy efficiency of CNNs. Compared with small crossbars, large crossbars show better energy efficiency with less interface overhead. However, conventional workload mapping methods for small crossbars cannot make full use of the computation ability of large crossbars. In this paper, we propose an Overlapped Mapping Method (OMM) and MIxed Size Crossbar based RRAM CNN Accelerator (MISCA) to solve this problem. MISCA with OMM can reduce the energy consumption caused by the interface circuits, and improve the parallelism of computation by leveraging the idle RRAM cells in crossbars. The simulation results show that MISCA with OMM can achieve 2.7x speedup, 30% utilization rate improvement, and 1.2x energy efficiency improvement on average compared with fixed size crossbars based accelerator using the conventional mapping method. In comparison with GPU platform, MISCA with OMM can perform 490.4x higher on average in energy efficiency and 20x higher on average in speedup. Compared with PRIME, an existing RRAM based accelerator, MISCA has 26.4x speedup and 1.65x energy efficiency improvement.