Tolerating Soft Errors in Deep Learning Accelerators with Reliable On-Chip Memory Designs

Deep learning neural network (DNN) accelerators have been increasingly deployed in many fields recently, including safety-critical applications such as autonomous vehicles and unmanned aircrafts. Meanwhile, the vulnerability of DNN accelerators to soft errors (e.g., caused by high-energy particle strikes) rapidly increases as manufacturing technology continues to scale down. A failure in the operation of DNN accelerators may lead to catastrophic consequences. Among the existing reliability techniques that can be applied to DNN accelerators, fully-hardened SRAM cells are more attractive due to their low overhead in terms of area, power and delay. However, current fully-hardened SRAM cells can only tolerate soft errors produced by single-node-upsets (SNUs), and cannot fully resist the soft errors caused by multiple-node-upsets (MNUs). In this paper, a Zero-Biased MNU-Aware SRAM Cell (ZBMA) is proposed for DNN accelerators based on two observations: first, the data (feature maps, weights) in DNNs has a strong bias towards zero; second, data flipping from zero to one is more likely to cause a failure of DNN outputs. The proposed memory cell provides a robust immunity against node upsets, and reduces the leakage current dramatically when zero is stored in the cell. Evaluation results show that when the proposed memory cell is integrated in a DNN accelerator, the total static power of the accelerator is reduced by 2.6X and 1.79X compared with the one based on the conventional and on state-of-the-art full-hardened memory cells, respectively. In terms of reliability, the DNN accelerator based on the proposed memory cell can reduce 99.99% of false outputs caused by soft errors across different DNNs.