A distributed I/O architecture for HARTS

摘要

The issue of I/O device access in HARTS --- a distributed real-time computer system under construction at the Real-Time Computing Laboratory (RTCL), The University of Michigan --- is explicitly addressed. Several candidate solutions are introduced, explored, and evaluated according to cost and complexity, reliability, and performance: (1) "node-direct" distribution with the intra-node bus and a local I/O bus, (2) use of dedicated I/O nodes which are placed in the hexagonal mesh as regular applications nodes but which provide I/O services rather than computing services, and (3) use of a separate I/O network which has led to the proposal of an "interlaced" I/O network. The interlaced I/O network is intended to provide both high performance without burdening node processors with I/O overhead as well as a high degree of reliability. Both static and dynamic multi-ownership protocols are developed for managing I/O device access in this I/O network. The relative merits of the two protocols are explored and the performance and accessibility which each provide are simulated.