Future avionics systems will have distributed architectures requiring computers and data transfer systems that can perform real-time calculations and are fault tolerant. Previously developed data bus standards such as MIL-STD-1553 are inadequate for these applications.Existing standards will not meet the needs of the future. They are too slow; have functions that are single-point failures; do not take advantage of new technologies such as fiber optics; and have poor efficiency when applied to distributed architectures.To meet the needs of data buses for distributed, real-time, fault-tolerant architectures of the future, a candidate High-Speed Data Bus (HSDB) protocol has been developed by the authors.This paper describes the performance characteristics of the candidate HSDB protocol including the following: Token-passing protocol. Token-passing best meets the needs because it is inherently distributed. Fiber optics implementation. Fiber optics is the media of choice because of its gready improved data rate, weight, and EMI characteristics. Host interface. The host interface is examined with respect to its interaction with the HSDB terminal. Performance against the HART benchmarks. The candidate HSDB protocol performs very well when it is evaluated against the SAE AE-9B High-Speed Data Bus Applications Requirements Task (HART) group developed benchmarks.