Shift-CIM: In-SRAM Alignment To Support General-Purpose Bit-level Sparsity Exploration in SRAM Multiplication

Multiplication plays a critical role in SRAM-based Computing-in-Memory (CIM) architectures. However, current SRAM-based CIMs face three major limitations. First, they do not fully exploit bit-level sparsity, resulting in unnecessary overhead in both latency and energy consumption. Second, the generation of numerous zero-dot products is superfluous. Third, the irregular organization of SRAM complicates the implementation. To address these issues, we propose Shift-CIM, a general-purpose approach that fully leverages bit-level sparsity within SRAM-based multiplications. Shift-CIM aligns the multipliers within the SRAM array, accumulating only the required dot products based on the non-zero bits of the multipliers. Shift-CIM achieves a regular SRAM organization by assembling two irregular SRAM arrays in a transposed manner. Our evaluations show that Shift-CIM is highly efficient, operating at a supply voltage of 0.9 V and a frequency of 833 MHz, while incurring only a 4.8% area overhead. Despite these modest requirements, Shift-CIM significantly accelerates multiplication operations, achieving up to 3.08× the performance improvement and a 60% reduction in energy consumption compared to state-of-the-art designs.