BIMAX: A Bitwise In-Memory Accelerator Using 6T-SRAM Structure

In-memory computing (IMC) paradigm reduces costly and inefficient data transfer between memory modules and processing cores by implementing simple and parallel operations inside the memory subsystem. SRAM, the fastest memory structure in the memory hierarchy, is an appropriate platform to implement IMC. However, the main challenges of implementing IMC in SRAM are the limited operations and unreliable accuracy due to environmental noise and process variations. This work proposes a low-latency, energy-efficient, and noise-robust IMC technique, called Bitwise In-Memory Accelerator using 6T-SRAM Structure (BIMAX). BIMAX performs parallel bitwise operations (i.e., (N)AND, (N)OR, NOT, X(N)OR) as well as row-copy with the capability of writing the computation result back to a target memory row. BIMAX functionality is based on an imbalanced differential sense amplifier (SA) that reads and writes data from and into multiple 6T-SRAM cells. The simulations show BIMAX performs these operations with 52.7% lower energy dissipation compared to the state-of-the-art IMC technique, with 5.7% average higher performance rate. Furthermore, BIMAX is about 5.4× more robust against environmental noises compared to the state-of-the-art.