The design of digital machines tolerant of soft errors /

This thesis deals primarily with the problem of soft-error tolerance in digital machines. The possible sources of soft errors are reviewed. It is shown that the significance of ionizing radiation increases with the scaling down of MOS technologies. The characteristics of electromagnetic interference sources are also discussed. After presenting the conventional methods of dealing with soft errors, a new approach to this problem is suggested. The new approach, called Soft-Error Filtering (SEF), consists of filtering every output of the logic before latching it, in such a way that a transient injected into a machine does not change the final result of an operation. An analysis of the reduction in the error rate that is obtained by using SEF is presented. For example, this analysis demonstrates that the error rate due to alpha particles generated by the decay of radioactive elements becomes negligible. A great deal of attention is devoted to the design of filtering latches which is an essential component for implementing SEF machines. Three structures are considered and a CMOS implementation is proposed in each case. The double-filter latch is the best of the three implementations. It features a nearly optimum performance in the time domain and it is relatively insensitive to process fluctuations. An overhead analysis demonstrates that SEF usually results in a small overhead, both in area and in time simultaneously. In conclusion, SEF is the best approach to the problem of designing a machine tolerant to short transients