Reliability-aware exceptions: tolerating intermittent faults in microprocessor array structures

In future technology nodes, reliability is expected to become a first-order design constraint. Faults encountered in a chip can be classified into three categories: transient, intermittent, and permanent. Fault classification allows a chip to take the appropriate corrective action. Mechanisms have been proposed to distinguish transient from non-transient faults where all non-transient faults are handled as permanent. Intermittent faults induced by wearout phenomena have become the dominant reliability concern in nanoscale technology, yet there is no mechanism that provides finer classification of non-transient faults into intermittent and permanent faults. In this paper, we present a new class of exceptions called Reliability-Aware Exceptions (RAEs) which provide the ability to distinguish intermittent faults in microprocessor array structures. The RAE handlers have the ability to manipulate microprocessor array structures to recover from all three categories of faults. Using RAEs, we demonstrate that the reliability of two representative microarchitecture structures, load/store queue and reorder buffer in an out-of-order processor, is improved by average factors of 1.3 and 1.95, respectively.