Single Event Functional Interrupt (SEFI) Sensitivities of a Multicore Microprocessor

This work presents the test results of 200 MeV proton irradiation campaigns in the BCM2711 processor with the multicore Cortex-A72 (A72), which is mounted on the Raspberry Pi 4 model B board. Only the single event functional interrupt (SEFI) vulnerabilities of the Cortex-A72 were quantified. The microprocessor was exercised with five software benchmarks to quantify the SEFI cross-sections. All benchmarks were executed on top of the Linux OS at a clock frequency of 700 MHz. We observed two types of SEFI events: halts/crash (no error message is provided before the system can no longer execute the benchmark), and OS system exception handler messages. The Raspberry Pi is an economical platform that can be used to research SEE mechanisms of high performance complex systems. The results of this work could help to understand how to reduce the complexity of the Linux OS for non-essential tasks to reduce SEFI event sensitivities. A total of 189 SEFI events were captured. The SEFI cross-section when only the OS kernel tasks exercise the A72 indicates that the most sensitive software is the OS kernel. The test data results for this work show that when the Cortex-A72 parallelizes a benchmark across the four CPUs, the SEFI cross-section decreases in comparison to when a benchmark is executed serially with a single CPU. In this case the lower SEFI cross-section when the workload is parallelized across the four CPUs could be because the number of kernel tasks per CPU is 3.3x lower in comparison to the number of kernel tasks when only one CPU is activated. The most-observed SEFI event with 43.4% occurrence rate was "unable to handle kernel paging request/or NULL pointer at virtual address." The mean work to a SEFI (MWTS) was also quantified, which is the average completed benchmarks before a SEFI event.