A Novel Transpose 2T-DRAM based Computing-in-Memory Architecture for On-chip DNN Training and Inference

Recently, DRAM-based Computing-in-Memory (CIM) has emerged as one of the potential CIM solutions due to its unique advantages of high bit-cell density, large memory capacity and CMOS compatibility. This paper proposes a 2T-DRAM based CIM architecture, which can perform both CIM inference and training for deep neural networks (DNNs) efficiently. The proposed CIM architecture employs 2T-DRAM based transpose circuitry to implement transpose weight memory array and uses digital logic in the array peripheral to implement digital DNN computation in memory. A novel mapping method is proposed to map the convolutional and full-connection computation of the forward propagation and back propagation process into the transpose 2T-DRAM CIM array to achieve digital weight multiplexing and parallel computing. Simulation results show that the computing power of proposed transpose 2T-DRAM based CIM architecture is estimated to 11.26 GOPS by a 16K DRAM array to accelerate 4CONV+3FC @100 MHz and has an 82.15% accuracy on CIFAR-10 dataset, which are much higher than the state-of-the-art DRAM-based CIM accelerators without CIM learning capability. Preliminary evaluation of retention time in DRAM CIM also shows that a refresh-less training-inference process of lightweight networks can be realized by a suitable scale of CIM array through the proposed mapping strategy with negligible refresh-induced performance loss or power increase.