Real-time scheduling support in Futurebus+

As real-time applications become more demanding, multiprocessors are being called upon to meet their increasingly stringent requirements. A simple but efficient architecture for building multiprocessors is to connect several processors to a common backplane bus. The backplane acts as a shared resource in this architecture and contention for its use by different bus modules must be resolved. In a real-time system, this backplane must also provide scheduling support such that the timing behavior of the resulting system is analyzable. In addition, the support primitives for real-time scheduling on a backplane bus must also be constrained by the economic considerations associated with a bus standard that is intended to support both time sharing and real-time applications. In this paper, we review the design considerations to support realtime systems in the IEEE Futurebus+ backplane specification and describe how this backplane can be used to satisfy timing constraints in priority-driven realtime systems.