Computational image sensors with CNN processing capabilities are emerging to alleviate the energy-intensive and time-consuming data movement between sensors and external processors. However, deploying CNN models onto these computational image sensors faces challenges from the limited on-chip memory resources and insufficient image processing throughput. This work proposes a 3D-stacked NAND flash-based computing-in-memory under image sensor architecture (CIMUS) to facilitate the complete deployment of CNN model. To fully leverage the potential of high bandwidth from the 3D-stacked integration, we design a novel distributed CNN mapping and dataflow to process the full focal plane image in parallel, which senses and recognizes ImageNet tasks with >1000fps. To tackle the computational error of inputs “0” in 3D NAND flash-based CIM, we propose an input-independent offset compensation method, which reduces the average vector-matrix multiplication (VMM) error by 48%. Evaluation results indicate that CIMUS architecture achieves a 9.8× improvement in CNN inference speed and a 33× boost in energy efficiency compared to the state-of-the-art computational image sensor in the ImageNet recognition task.

Nonvolatile-based computing-in-memory inference chips show great potential to accelerate convolutional neural networks. The intrinsic weight stationary characteristic makes pipeline design a crucial solution to further enhance throughput. In this work, we propose a balanced pipeline design and establish performance/area evaluation models for the optimal pipeline solution. The evaluation results indicate that our pipeline design achieves$30\times$computational efficiency improvement.

Computing in memory (CIM) convolutional neural network (CNN) accelerators based on nonvolatile memory (NVM) show great potential to improve energy efficiency and throughput, while the multiple design levels and huge design space of CIM-based CNN acceleration system make cross-level co-design methodology and platforms extremely desired. In this work, an algorithm-hardware co-design platform CoMN with the graphic user interface is proposed for designers to fast verify and further optimize the designments. In the platform, 1) a mapper is developed to automatically map CNN models to CIM chips through optimizing pipeline, weight transformation, partition, and placement; 2) accuracy evaluator and performance evaluator are built to jointly estimate accuracy, energy, latency, and area overheads considering the design dependencies across multiple levels; 3) algorithm adapter is exploited to retrain CNN weights for higher hardware accuracy within limited energy budget through nonidealities aware training and energy aware training; 4) hardware optimizer is developed to search hardware microarchitecture and circuit design space in the early design stage. We conduct several case studies to verify the effectiveness of the CoMN platform. Results indicate that CoMN platform can enable algorithm-hardware mapping, hardware-aware algorithm adaption, hardware configuration exploration, and overall algorithm-hardware co-design efficiently. The CoMN platform can be accessed online at http://101.42.97.22:8081/index.html with username “tcad” and password “comnuser”.

Non-volatile memory (NVM)-based Computation-in-memory has demonstrated a significant advantage in high-efficiency neural networks. However, the requirement of analog-to-digital converter (ADC) and post-processing circuits not only cost high energy and area but also results in high computation errors, which tradeoffs the performance boost brought by CIM. Here, we present a specific ADC and post-processing circuit of the NVM-based CIM neural network to address these issues. The main contributions include: (1) A novel residual charge accumulation function (RCA) is designed to achieve charge-domain summation of quantized partial sum and reduces 38% quantization error; (2) Charge reset is introduced in the integrate & fire circuit to realize$3.95\times $energy efficiency and$2.48\times $area efficiency. Evaluation based on the measured results of the fabricated chip shows that the VGG-11 neural network with the proposed ADC circuit can achieve a 3.28-time improvement in energy efficiency while maintaining the same network recognition rate.