Susceptible workload driven selective fault tolerance using a probabilistic fault model

Abstract

In this paper, we present a novel fault tolerance design technique, which is applicable at the register transfer level, based on protecting the functionality of logic circuits using a probabilistic fault model. The proposed technique selects the most susceptible workload of combinational circuits to protect against probabilistic faults. The workload susceptibility is ranked as the likelihood of any fault to bypass the inherent logical masking of the circuit and propagate an erroneous response to its outputs, when that workload is executed. The workload protection is achieved through a Triple Modular Redundancy (TMR) scheme by using the patterns that have been evaluated as most susceptible. We apply the proposed technique on LGSynth91 and ISCAS85 benchmarks and evaluate its fault tolerance capabilities against errors induced by permanent faults and soft errors. We show that the proposed technique, when it is applied to protect only the 32 most susceptible patterns, achieves on average of all the examined benchmarks, an error coverage improvement of 98% and 94% against errors induced by single stuck-at faults (permanent faults) and soft errors (transient faults), respectively, compared to a reduced TMR scheme that protects the same number of susceptible patterns without ranking them.

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