A deductive fault diagnosis method for resolving cases of test invalidation in multiprocessor systems

A new deductive fault-diagnosis method that resolves cases of test invalidation in multiprocessor systems is presented. The necessary conditions for PMC-based one-step t-fault diagnosability methods require that there are at least {dollar}2t + 1{dollar} processor nodes, and that each node is diagnosed by at least t other processor nodes. The Deductive Fault-Diagnosis (DFD) method shown in the present research shows the conditions under which these requirements can be eliminated. The DFD method assumes that for each processor PE{dollar}rmsb{lcub}i{rcub}{dollar} within a multiprocessor system M, the number of faults in {dollar}Isb{lcub}i{rcub}leq1{dollar} and the number of faults in {dollar}it Isbsp{lcub}i{rcub}{lcub}-1{rcub}geq0{dollar}. The set {dollar}Isb{lcub}i{rcub}{dollar} consists of the faults in processor PE{dollar}rmsb{lcub}i{rcub}{dollar} that affect the outcome of tests performed on an adjacent processor PE{dollar}rmsb{lcub}j{rcub}{dollar}. The set {dollar}it Isbsp{lcub}i{rcub}{lcub}-1{rcub}{dollar} is the set of faults in processor PE{dollar}rmsb{lcub}i{rcub}{dollar} that have no effect on the tests of processor PE{dollar}rmsb{lcub}j{rcub}{dollar}. The results are achieved by performing further analysis on the failures reported by both faulty and fault-free processors and by developing a Reverse Fault Dictionary (RFD) to help resolve cases of test invalidation. The RFD tabulates the effects of two forms of test invalidation: fault misdirecting and fault masking. Fault misdirecting occurs when a fault {dollar}fsb{lcub}d{rcub}{dollar} in processor PE{dollar}rmsb{lcub}i{rcub}{dollar} causes the test of a fault-free adjacent processor PE{dollar}rmsb{lcub}j{rcub}{dollar} to incorrectly report the presence of a fault {dollar}fsb{lcub}n{rcub}{dollar} in processor PE{dollar}rmsb{lcub}j{rcub}{dollar}. Fault masking occurs when a fault {dollar}fsb{lcub}m{rcub}{dollar} in processor PE{dollar}rmsb{lcub}i{rcub}{dollar} conceals the presence of a fault {dollar}fsb{lcub}n{rcub}{dollar} in an adjacent processor PE{dollar}rmsb{lcub}j{rcub}{dollar} causing processor PE{dollar}rmsb{lcub}i{rcub}{dollar} to incorrectly report the absence of fault {dollar}fsb{lcub}n{rcub}{dollar} in processor PE{dollar}rmsb{lcub}j{rcub}{dollar}. The diagnostic capabilities of this method are not limited by the number of faulty processors, but by the test invalidation relationships of faults within adjacent processors.