Self-timed carry-lookahead adders

Abstract

Integer addition is one of the most important operations in digital computer systems because the performance of processors is significantly influenced by the speed of their adders. This paper proposes a self-timed carry-lookahead adder in which the logic complexity is a linear function of n, the number of inputs, and the average computation time is proportional to the logarithm of the logarithm of n. To the best of our knowledge, our adder has the best area-time efficiency which is /spl Theta/(nloglogn). An economic implementation of this adder in CMOS technology is also presented. SPICE simulation results show that, based on random inputs, our 32-bit self-timed carry-lookahead adder is 2.39 and 1.42 times faster than its synchronous counterpart and self-timed ripple-carry adder, respectively, and, based on statistical data gathered from a 32-bit ARM simulator, it is 1.99 and 1.83 times faster than its synchronous counterpart and self-timed ripple-carry adder, respectively.