Designing reliable computer systems-the fault-tolerant approach - 2

This article is the second part of a two-part tutorial article on the design of fault-tolerant digital systems. The first part, published in November, presented the general principles of fault tolerance and discussed the use of redundancy to increase system reliability and availability. The article also commented on the design of self-testing logic circuits. In this second part, we concentrate more on what has been achieved in practice, and the article describes the JPL-Star computer. This is an experimental computer designed to evaluate many of the strategies for enhancing fault-tolerance, and it is already obsolete. This article concludes, therefore, with a brief survey of other fault-tolerant proposals and implementations