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Recent research has shown interest in adopting the RISC-V processors for high-reliability electronics, such as aerospace applications. The openness of this architecture enables the implementation and customization of the processor features to increase their reliability. Studies on hardened RISC-V processors facing harsh radiation environments apply fault tolerance techniques in the processor core and peripherals, exploiting system redundancies. In prior work, we present a hardened RISC-V System-on-Chip (SoC), which could detect and correct radiation-induced faults with limited fault awareness. Therefore, in this work, we propose solutions to extend the fault observability of the SoC implementation by providing error detection and monitoring. For this purpose, we introduce observation features in the redundant structures of the system, enabling the report of valuable information that supports enhanced radiation testing and support the application to perform actions to recover from critical failures. Thus, the main contribution of this work is a solution to improve fault awareness and the analysis of the fault models in the system. In order to validate this solution, we performed complementary experiments in two irradiation facilities, comprehending atmospheric neutrons and a mixed-field environment,in which the system proved to be valuable for analyzing the radiation effects on the processor core and its peripherals.In these experiments, we were able to obtain a range of error reports that allowed us to gain a deeper understanding of the faults mechanisms, as well as improve the characterization of the SoC.

The radiation in harsh environments affects electronic systems, inducing permanent and temporary errors. These effects lead to unpredictable behaviors detrimental to critical applications and fail-safe systems. This work evaluates the reliability of a fault-tolerant RISC-V System-on-Chip (SoC) under atmospheric neutron irradiation in a particle accelerator. Prior work has analyzed the effectiveness of the hardening techniques of this SoC in simulation and provided a preliminary characterization in an irradiation facility. The applied hardening techniques showed a significant reliability improvement compared to the unhardened implementation of the SoC. The system executed a performance benchmark as workload, which finished correctly in most runs despite suffering from Single Event Effects (SEEs). This work presents a detailed analysis of the experimental results, reporting error rates and classification, extending the analysis given in previous works. Finally, a comprehensive discussion of implementation limitations and the proposition of further improvements are provided.