Implementation of 32-bit Ling and Jackson Adders

Ling adders factor complexity out of the first stage of an adder to shorten the critical path. In 2004, Jackson and Talwar proposed a generalization of the Ling adder that reduces the complexity of the critical generate path at the expense of increased complexity in the propagate logic. This paper compares implementations of 32-bit Ling and Jackson adders to the optimized Sklansky architecture produced by Design Compiler in a 45 nm process. The Ling adder is 3% faster and uses 7% less energy, achieving a delay of 8.3 FO4 inverters. The Jackson adder is only 1% faster and uses 45% more energy. However, this is the first published implementation of a Jackson adder with all details shown.