PABLO: A Variation-Robust PIM Architecture for Bulk Bitwise Logical Operations in DRAM

The significant data movement between processing units and DRAM adversely affects the performance and energy efficiency of the systems to process bulk bitwise logical operations (BLOs). Researchers have addressed the problem by employing processing-in-memory (PIM) techniques, where bulk bitwise operations are processed in DRAM. Among existing techniques, semi-digital PIMs, which support bulk BLOs by utilizing DRAM core circuits, are one of the most viable designs due to their moderate area penalties. However, our study reveals that state-of-the-art (SOTA) semi-digital PIMs suffer from considerable computation errors caused by process variations. This paper presents PABLO, a novel PIM architecture based on DRAM, to address the challenge. The essential contribution is to develop a generic bitwise unit integrated with the conventional local sense amplifier, enabling bulk BLOs with minimal overhead and modifications of commodity DRAM. As a result, the proposed design allows for simplified bitwise operations while hardly affecting conventional DRAM core operations. We comprehensively demonstrate the enhanced variation tolerance of PABLO compared to SOTA semi-digital PIMs through Monte Carlo simulations. Furthermore, our evaluation results indicate that PABLO achieves a speedup of up to $\sim 3.97\times$ and energy savings of up to $\sim 3.87\times$ compared to existing solutions.