1. A method for switching to a spare processor during runtime, the method comprising: determining that execution should be migrated off of an active processor in a processing system; after determining that execution should be migrated off of the active processor, pausing an operating system (OS) scheduler in the processing system, pausing at least one device in the processing system, and putting the active processor into an idle state; saving state data from writable and substantial non-writable stores in the active processor, to a store outside of the active processor, starting a spare processor in the processing system; loading the state data saved from the writeable store of the active processor to the spare processor; loading the state data saved from the substantially non-writeable store of active processor to the spare processor; reprogramming interrupt routing table logic for the processing system to direct external interrupts to the spare processor; off-lining the active processor; resuming the device; and resuming the OS scheduler.