Successful use of rate monotonic theory on a formidable real time system

The navigation payload software for the next block of Global Positioning System satellites recently completed testing. The computer program for the onboard computer is sufficiently complex to expose almost every issue that has been put forward in rate monotonic theory. The success of this effort demonstrates the utility of the theory in this type of application. The system designed required the processor to perform a highly diverse set of hard deadline real-time functions. This design would have been difficult or impossible prior to the development of rate monotonic theory. The use of utilization bounds has important advantages from a software engineering point of view. The problems of insuring schedulability over the course of development and verifying the schedulability of the finished system are discussed