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Computational Efficiency of Two-Operand Adders

IP.com Disclosure Number: IPCOM000061820D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Sinha, B: AUTHOR

Abstract

This article describes a method to determine the efficiency of two- operand adders. Given the requirement of an n-bit adder, the most efficient algorithm can be chosen by utilizing this method. The existing method for obtaining the efficiency of two-operand adders is explained in [*]. The method disclosed herein proposes a new measure of efficiency of two-operand adders in today's technology and compares some of the standard adders used in present arithmetic logic unit (ALU) designs. This method has been developed with the following two guidelines in mind: 1. Efficiency , however formulated, is only good as a relative measure. 2. Efficiency should be simple, and convey some meaningful means of comparison between schemes for achieving similar processes, i.e., between various adder schemes.

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Computational Efficiency of Two-Operand Adders

This article describes a method to determine the efficiency of two- operand adders. Given the requirement of an n-bit adder, the most efficient algorithm can be chosen by utilizing this method. The existing method for obtaining the efficiency of two-operand adders is explained in [*]. The method disclosed herein proposes a new measure of efficiency of two-operand adders in today's technology and compares some of the standard adders used in present arithmetic logic unit (ALU) designs. This method has been developed with the following two guidelines in mind: 1. Efficiency , however formulated, is only good as a relative measure. 2. Efficiency should be simple, and convey some meaningful means of comparison between schemes for achieving similar processes, i.e., between various adder schemes. Based on this, the following measure is disclosed:

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This gives complexity and delay (inputs) the same relative weight as each other, and as the number of bits (output). The square root is used to give inputs and outputs the same order of dependence. Since ripple-carry is the well-known straightforward method and the other methods are designed as improvements on it, its efficiency is constant with changing n.

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This new measure of efficiency takes into account the fact that a circuit may cost less than its component gates. This can also apply to large sale integration (LSI) and very large scale integratio...