A Comprehensive Comparative Analysis of Parallel Prefix Adders for ASIC Implementation

Abstract

Parallel Prefix Adders are the most common choice for fast adders. The design of efficient adder is always a compromise between the parameters such as area and delay. This paper discuss the comparison and performance analysis of different parallel prefix adders on the basis of these performance parameters, and thereby providing an option for selecting the most appropriate adder topology for ASIC implementations. The tree adder topologies considered in this work are Kogge- Stone, Ladner-Fischer, Brent-Kung and Sklansky adders. The comparison is performed for bit widths ranging from 16 bits to 1024 bits. Along with the comparison of conventional tree adders, an attempt is made to study the effect of sectioning of the data into different blocks, and thus performing additions at section level and cascading them as in a ripple carry adder. Over the complete range from 16 bits to 1024 bits, Kogge-Stone adder has the best delay performance and Brent- Kung adder has the best performance (excluding RCA) in terms of area and power. Kogge-Stone adder has the minimum area-delay product for small values of N, while for medium to large values of N (up to 1024 bits), Brent-Kung adder show minimum value.