An expert system to perform functional diagnosis of a bus subsystem

AGATHA is an expert system designed to assist in the test and diagnosis of Hewlett-Packard PA-RISC processor boards during manufacturing. It consists of several smaller cooperating expert systems, called slices, capable of diagnosing different parts of a circuit board. The authors focus on the slice responsible for diagnosing the cachebus subsystem, outlining its design and performance. This slice diagnoses failures on an electronic bus by processing a large quantity of test data. Rather than using heuristics, it uses a causal rule-based approach, and it is able to handle intermittent faults and also most situations involving multiple faults. Updating the system to handle new boards is made easier by separating board-specific knowledge from test-specific knowledge and the process is now automated. The system has been deployed and is in regular use at three sites