A computer system comprises an active processor and one or more spare processors. A dummy thread is created on the active processor while the active processor is running a current thread, causing the current thread to become dormant. The operating system of the active processor saves a set of internal state information for the current thread into a first memory coupled to the active processor. Each write to the first memory is duplicated in an equivalent spare memory coupled to each of the one or more spare processors. The dummy thread then activates the spare processor and de-activates the active processor.