High-speed, energy-efficient 2-cycle Multiply-Accumulate architecture

Abstract

We propose a high-speed and energy-efficient 2-cycle Multiply-Accumulate (MAC) architecture. Our architecture is based on two's complement representation, it uses guarding bits to efficiently support longer MAC loops, and it includes output saturation. By performing carry propagation only in the second stage of the MAC pipeline, multiplication and accumulation have similar delays. But in contrast to previous MAC architectures that propose to only use one carry-propagation stage, our architecture requires no extra cycles to produce the final result. Instead it correctly produces the sum of the accumulated value and the product in each cycle. Our place-and-route evaluation shows that the proposed architecture, averaged across several operand sizes, offers a 33% improvement in speed and a 37% reduction of energy over a conventional 2-cycle MAC architecture.