AiDAC: A Low-Cost In-Memory Computing Architecture with All-Analog Multi-Bit Compute and Interconnect

Analog in-memory computing (AiMC) is an emerging technology that shows fantastic performance superiority for neural network acceleration. However, as the computational bit-width and scale increase, high-precision data conversion and long-distance data routing will result in unacceptable energy and latency overheads in the AiMC system. In this work, we focus on the potential of in-charge computing and in-time interconnection and show an innovative AiMC architecture, named AiDAC, with three key contributions: (1) AiDAC enhances multibit computing efficiency and reduces data conversion times by grouping capacitors technology; (2) AiDAC first adopts row drivers and column time accumulators to achieve large-scale AiMC arrays integration while minimizing the energy cost of data movements. (3) AiDAC is the first work to support large-scale all-analog multibit vector-matrix multiplication (VMM) operations. The evaluation shows that AiDAC maintains high-precision calculation (less than 0.79% total computing error) while also possessing excellent performance features, such as high parallelism (up to 26.2TOPS), low latency (<20ns/VMM), and high energy efficiency (123.8TOPS/W), for 8bits VMM with 1024 input channels.