Run-time Instruction Replication for permanent and soft error mitigation in VLIW processors

Abstract

Error occurrence in embedded systems has significantly increased. Although inherent resource redundancy exist in processors, such as in Very Long Instruction Word (VLIW) processors, it is not always used due to low application's Instruction Level Parallelism (ILP). Approaches benefit the additional resources to provide fault tolerance. When permanent and soft errors coexist, spare units have to be used or the executed program has to be modified through self-repair or by using several stored versions. However, these solutions introduce high area overhead for the additional resources, time overhead for the execution of the repair algorithm and storage overhead of the multiversioning. To address these limitations, a hardware mechanism is proposed which at run-time replicates the instructions and schedules them at the idle slots considering the resource constraints. If a resource becomes faulty, the proposed approach efficiently rebinds both the original and replicated instructions during execution. In this way, the area overhead is reduced, as no spare resources are used, whereas time and storage overhead are not required. Results show up to 49% performance gain over existing techniques.

Fine-Grained Hardware Mitigation for Multiple Long-Duration Transients on VLIW Function Units

“…We compare the performance with existing online coarsegrained approaches, such as [9]. In contrast to the proposed fine-grained approach, the coarse-grained approach neither 1) explores the FUs in fine-grained way nor 2) applies temporal exclusion.…”

“…However, they perform coarse-grained exploration, i.e. the faulty complex FUs can still be used as simple FUs, whereas the faulty part is permanently excluded for the rest of the execution [9].…”

Run-Time Coarse-Grained Hardware Mitigation for Multiple Faults on VLIW Processors

“…However, instruction duplication and re-execution approaches [7] and run-time rescheduling mechanisms [8] have not been explored for multiple errors. The work in [9] applies duplication and triplication of the instructions for multiple errors, whereas a mechanism is proposed to exclude the faulty FUs permanently for the rest of the execution. However, the negative impact on performance is significant.…”