Exploiting Instruction Set Encoding for Aging-Aware Microprocessor Design

摘要

Microprocessors fabricated at nanoscale nodes are exposed to accelerated transistor aging due to bias temperature instability and hot carrier injection. As a result, device delays increase over time, reducing the mean time to failure (MTTF) and hence lifetime of the processor. To address this challenge, many (micro)architectural techniques target the execution stage of the instruction pipeline, as this one is typically most critical. However, also the decoding stages can become aging critical and limit the microprocessor lifetime, as we will show in this work. Therefore, we propose a novel aging-aware instruction set-encoding methodology (ArISE) that improves the instruction encoding iteratively using a heuristic algorithm. In addition, the switching activities of the affected memory elements are considered in order to co-optimize lifetime and energy efficiency. Our experimental results show that MTTF of the decoding stages can be improved by 2.3x with negligible implementation costs.