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Statistical Carry Lookahead Adders
March 1996 (vol. 45 no. 3)
pp. 340-347

Abstract—Addition techniques are divided into fixed-time and variable-time ones. While variable time techniques can achieve log2(N) average addition time for N-bit operands, the hardware overhead have always made fixed-time adders preferable, such as Carry Lookahead and Carry Select.

We present a new variable-time addition technique whose average delay is much lower than log2(N) and whose overhead is lower than the one of a CLA adder. The new approach is made feasible by a proper application of VLSI dynamic logic design. We show the mathematical proof, the logic implementation, and the VLSI realization of the new adder. We report circuit simulation results and their comparison with the analytical model.

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Index Terms:
Self-timed systems, computer arithmetic, asynchronous circuits, VLSI design, completion detecting units.
Alessandro De Gloria, Mauro Olivieri, "Statistical Carry Lookahead Adders," IEEE Transactions on Computers, vol. 45, no. 3, pp. 340-347, March 1996, doi:10.1109/12.485572
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