While Moore's law scaling continues to double transistor density every technology generation, new design challenges are introduced. One of these challenges is variation, resulting in deviations in the behavior of transistors, most importantly in switching delays. These exaggerated delays widen the gap between the average and the worst case behavior of a circuit. Conventionally, circuits are designed to accommodate the worst case delay and are therefore becoming very limited in their performance

more »

... advantages. Thus, allowing for an average case oriented design is a promising solution, maintaining the pace of performance improvement over future generations. However, to maintain correctness, such an approach will require on the fly mechanisms to prevent, detect, and resolve violations. This paper explores such mechanisms, allowing the improvement of circuit performance under intensifying variations. We present speculative error detection techniques along with recovery mechanisms. We continue by discussing their ability to operate under extreme variations including sub-threshold operation. While the main focus of this survey is on circuit approaches, for its completeness, we discuss higher-level, architectural and algorithmic techniques as well.