Exploiting instruction redundancy for transient fault tolerance [microprocessor applications]

This paper presents an approach for integrating fault-tolerance techniques into microprocessors by utilizing instruction redundancy as well as time redundancy. Smaller and smaller transistors, higher and higher clock frequency, and lower and lower power supply voltage reduce the reliability of microprocessors. In addition, microprocessors are used in systems which require high dependability, such as e-commerce businesses. Based on these trends, it is expected that the quality with respect to reliability will become important as well as performance and cost for future microprocessors. To meet the demand, we have proposed and evaluated a fault-tolerance mechanism, which is based on instruction reissue and utilizes time redundancy, and found severe performance loss. In order to mitigate the loss, this paper proposes to exploit instruction redundancy. Using the reuse table, previously executed computing is reused for checking the occurrence of transient faults. From detailed simulations, we find that the performance loss caused by introducing fault tolerance into 4-way and 8-way superscalar processors is 12.5% and 20.8%, respectively.