An unprotected RISC-V Soft-core processor on an SRAM FPGA: is it as bad as it sounds?

Fast development, low cost, and reconfigurability are becoming critical factors for aerospace applications, making SRAM FPGAs attractive. However, SRAM FPGAs are prone to errors in the user and on the configuration bits. For their correct functioning, they must be capable of withstanding failures without sacrificing much performance. When adjusting a soft core for these applications, it is essential to know where redundancies are necessary, to avoid unnecessary overhead. We characterize the reliability of an unprotected RISC-V microcontroller using an accelerated neutron beam. Our investigation shows that, for our chosen benchmark and processor, the user data in the memory banks is the leading cause of the total number of errors in the application. By reversing the benchmark operations, we could root cause the origin of the observed errors and found that most of the data corruption detected during the runs stem from previously corrupt input data or from output data that were corrupted while transmitting.