History index of correct computation for fault-tolerant nano-computing

Future nanoscale devices are expected to be more fragile and sensitive to external influences than conventional CMOS-based devices. Researchers predict that it will no longer be possible to test a device and then throw it away if it is found to be defective, as every circuit is expected to have multiple hard and soft defects. Fundamentally new fault-tolerant architectures are required to produce reliable systems that will survive with manufacturing defects and transient faults. This paper introduces the History Index of Correct Computation (HICC) as a run-time reconfiguration technique for fault-tolerant nano-computing. This approach identifies reliable blocks on-the-fly by monitoring the correctness of their outputs and forwarding only good results, ignoring the results from unreliable blocks. Simulation results show that history-based TMR modules offer a better response to fault tolerance at the module level than do conventional fault-tolerant approaches when the faults are nonuniformly distributed among redundant units. A correct computation rate of 99% is achieved despite a 13% average injected fault rate, when one of the redundant units and the decision unit are fault-free as well as when both have a low injected fault rate of 0.1%. A correct computation rate of 89% is achieved when faults are nonuniformly distributed at an average fault rate of 11% and fault rate in the decision unit is 0.5%. The robustness of the history-based mechanism is shown to be better than both majority voting and a Hamming detection and correction code.