A tagged memory technique for recovery from transient errors in fault tolerant systems

Recovery from transients is imperative to maintain necessary system reliability in the face of transient errors which have been estimated to occur at a rate of 5 to 100 times that of permanent failures. Excessive delays associated with recovery become a problem when as much as 512 Kbytes of RAM in the faulty processor must be restored while maintaining full functionality of 40-100 Hz iterative control algorithms. The authors introduce a hardware-assisted recovery technique which uses memory `tags´ to determine which memory segments need to be restored such that recovery can be performed incrementally without affecting real-time operational tasks. They also present experimental results of an implementation of this technique applied to a quad redundant processor with a partial code suite for an undersea vehicle