Microprocessor-based systems are the most common design for high-performance computing (HPC) platforms. In these systems, several thousands of microprocessors can participate in a single calculation that could take weeks or months to complete. When used in this manner, a fault in any of the microprocessors could cause the computation to crash or cause silent data corruption (SDC), i.e.~computationally incorrect results. In recent years, neutron-induced failures in HPC hardware have been observed, and researchers have started to study how neutron radiation affect microprocessor-based scientific computations. This paper presents results from an accelerated neutron test focusing on two microprocessors used in Roadrunner, the first Petaflop system.