Energy-Efficient In-SRAM Accumulation for CMOS-based CNN Accelerators

State-of-the-art convolutional neural network (CNN) accelerators are typically communication-dominate architectures. To reduce the energy consumption of data accesses and also to maintain the high performance, researches have adopted large amounts of on-chip register resources and proposed various methods to concentrate communication on on-chip register accesses. As a result, the on-chip register accesses become the energy bottleneck. To further reduce the energy consumption, in this work we propose an in-SRAM accumulation architecture to replace the conventional register files and digital accumulators in the processing elements of CNN accelerators. Compared with the existing in-SRAM computing approaches (which may not be targeted at CNN accelerators), the presented in-SRAM computing architecture not only realizes in-memory accumulation, but also solves the structure contention problem which occurs frequently when embedding in-memory architectures into CNN accelerators. HSPICE simulation results based on the 45nm technology demonstrate that with the proposed in-SRAM accumulator, the overall energy efficiency of a state-of-the-art communication-optimal CNN accelerator is increased by 29% on average.