VLSI Implmentation of a Fast Kogge-Stone Parallel-Prefix Adder

Abstract

This paper presents a VLSI implementation of a high speed Kogge-Stone adder (KSA) using 0.18μm process technology. The adder is known to be one of the fastest adder architectures, and this is validated through a comparison with other adder architectures including the standard ripple carry adder and the carry look ahead adder. Furthermore, our KSA adder is also compared with a default optmized adder from the Artisan standard cell library. The adders are compared for bit widths of 8, 16, and 32. The adders are designed using Verilog and synthesized using both front-end and back-end tools, with complete validation and verification stages, including analysis for performance, power, and area. Results show that in terms of performance, KSA results in the lowest propagation delay with almost constant delay for all bit widths, with up to 70% less delay as compared to all other architectures. Area and power penalty is found to also increase by roughly 59%. In terms of energy usage, the KSA adder results in up to 64% less. In the case when speed and energy are critical, this fast and energy efficient KSA adder can be readily integrated into custom VLSI designs.