A general approach for highly defect tolerant parallel prefix adder design

This paper proposes a highly defect tolerant Parallel Prefix Adder (PPA) design. Motivated by the inherent defect tolerance capability displayed in a Kogge Stone Adder (KSA), this paper identifies the key elements that can be applied to make the general PPA's defect tolerant: 1) the Generate and Propagate computing hardware is divided into disjoint groups, such that defects in one group will not “contaminate” the computation carried out by the other groups; 2) redundant copies of the results for each group can be derived cost-effectively from the other disjoint groups. This approach provides flexibilities for a defect tolerant PPA design on both the number of groups and the type of Sub-Adder structure to be adopted. As is verified by the simulation results, the proposed scheme not only offers a general way of constructing highly defect tolerant PPA's, but also opens up a large number of pareto-front design choices, considering the objectives of reliability, hardware and performance.