Stochastic Computing

As device sizes shrink, manufacturing challenges at the device level are resulting in increased variability in physical circuit characteristics. Exponentially increasing circuit density has not only brought about concerns in the reliable manufacturing of circuits but also has exaggerated variations in dynamic circuit behavior. The resulting uncertainty in performance, power, and reliability imposed by compounding static and dynamic nondeterminism threatens the continuation of Moore’s law, which has been arguably the primary driving force behind technology and innovation for decades. This situation is exacerbated by emerging computing applications, which exert considerable power and performance pressure on processors. Paradoxically, the problem is not nondeterminism, per se, but rather the approaches that designers have used to deal with it. The traditional response to variability has been to enforce determinism on an increasingly non-deterministic substrate through guardbands. As variability in circuit behavior increases, achieving deterministic behavior becomes increasingly expensive, as performance and energy penalties must be paid to ensure that all devices work correctly under all possible conditions. As such, the benefits of technology scaling are vanishing, due to the overheads of dealing with hardware variations through traditional means. Clearly, status quo cannot continue.