Fine-Grained Fault Tolerance for Process Variation-Aware Caches

Abstract

Continuous scaling in CMOS fabrication process makes circuits more vulnerable to process variations, which results in variable delay, malfunctioning, and/or leaky circuits. Caches are one of the biggest victims of process variations due to their large sizes and minimal cell features. To mitigate the impacts of process variations on caches, we propose to localize the effects of process variations at a word level, not at the conventional cache set, cache way, or cache line level. Faulty words are disabled or shut down completely and accesses to those words are bypassed to a small set of word-length buffers. This technique is shown to be effective in reducing performance penalty due to process variations and in increasing the parametric yield up to 90% when subjected to the performance constraints.