New pulse klystron amplifier for the 960–1, 215-megacycle region

Abstract

rant the added expense of building and maintaining it.This decision is based on the expectation that a comput ing machine should operate 95 per cent of total time or better and that the average time between random failures should be of the order of 5 to 10 hours, or approximately 10 9 operations.In our opinion, the way to achieve the extremely high reliability needed in some real-time control problems is to provide three or more identical but distinct machines, thus obtaining error correction as well as detection, plus such features as stand-by, safety, and damage control. Even so the failure probability of each machine must be kept low by proper design, marginal checking, and pre ventive maintenance.Extremely high reliability means a reliability far beyond that achieved in existing machines and not conveniently represented as a per cent. Consider a system consisting of three machines, each operable 98 per cent of the time and each averaging 10 hours between random errors.One machine will be out of operation 1 /2 hour per day. Two machines will be out of operation 1/4 hour per month. All three machines will be out of operation 4 minutes per year. Furthermore, undetected random errors might occur on the average of once a year. Such reliability is needed in some systems.The decision to omit detailed checking does not extend to checking devices intended to detect programming errors. Devices to check for overflow from the arithmetic element or for nonexistent order configurations are necessary. Programmers make many mistakes. Techniques for dealing with programming errors are very important and they are in need of considerable further development.