Design and characterization of NULL convention arithmetic logic units

In this paper, a number of 4-bit, 8-operation arithmetic logic units (ALUs) are designed using the delay-insensitive NULL convention logic paradigm, and are characterized in terms of speed and area. Both dual-rail and quad-rail, pipelined and non-pipelined versions are developed, and the tradeoffs and design considerations for each are discussed. Comparing the various architectures shows that the fastest dual-rail and quad-rail ALUs achieve average speedups of 1.72 and 1.59, respectively, over their non-pipelined counterparts, while requiring 133% and 119% more area, respectively. Overall, the dual-rail designs are both faster and require less area than their respective quad-rail counterparts; however, the quad-rail versions are expected to consume less power.