Radiation Specification and Testing of Heterogenous Microprocessor SOCs

Modern commercial microprocessor devices include multiple processor architectures, buses, basic peripherals, and application hardware such as Graphics Processing Units (GPUs) and Digital Signal Processors (DSPs) in one device. Developing RHBD versions of similar devices risks sacrificing processing performance for system-wide radiation requirements. The heterogenous structure of modern commercial system on a chip (SOC) devices, in design and performance goals for subsystems, suggests a similar approach to specifying Radiation Hardened by Design (RHBD) requirements. New RHBD devices can benefit from heterogenous radiation requirements and testing for subsystems. Such an approach has been taken in the High-Performance Spaceflight Computer (HPSC) architecture, but this has led to difficulties on three fronts. First, how should the subsystems be divided in order that part of the device can actually meet radiation requirements in the presence of potentially much weaker requirements for other parts of the system? Second, what are appropriate radiation requirements for such a device, including a possible extra-radiation hardened embedded controller? And finally, how should a device with multiple radiation performance subsystem requirements be tested for radiation performance?