Combating Aging with the Colt Duty Cycle Equalizer

Bias temperature instability, hot-carrier injection, and gate-oxide wear out will cause severe lifetime degradation in the performance and the reliability of future CMOS devices. The design guard band to counter these negative effects will be too expensive, largely due to the worst-case behavior induced by the uneven utilization of devices on the chip. To mitigate these effects over a chip´s lifetime, this paper proposes Colt, a simple yet holistic scheme to balance the utilization of devices in a processor by equalizing the duty cycle ratio of circuits´internal nodes and the usage frequency of devices. Colt relies on alternating true-and complement-mode operations to equalize the duty cycle ratio of signals (thus the utilization of devices) in most data path and storage devices. Colt also employs a pseudorandom indexing scheme to balance the usage of entries in storage structures that often exhibit highly uneven utilization of entries. Finally, an operand-swapping scheme equalizes utilization of the left and right operand data paths. The proposed mechanisms impose trivial overhead in area, complexity, power, and performance, while recapturing 27% of aging-induced performance degradation and improving meantime to failure by an estimated 40%.