Power supply induced common cause faults-experimental assessment of potential countermeasures

Fault-tolerant architectures based on physical replication of components are vulnerable to faults that cause the same effect in all replica. Short outages in a power supply shared by all replica are a prominent example for such common cause faults. For systems in which the provision of a replicated power supply would cause prohibitive efforts the identification of reliable countermeasures against these effects is vital to maintain the required dependability level. In this paper we propose several of such countermeasures, namely parity protection, voltage monitoring and time diversity of the replica. We perform extensive fault injection experiments on three fault-tolerant dual core processor designs, one FPGA based and two commercial ASICs. These experiments provide evidence for the vulnerability of a completely unprotected dual core solution, while time diversity and voltage monitoring in combination with increased timing margins turn out particularly effective for eliminating common cause effects.