A system for general-purpose analog-digital computation

Abstract

Concerning the age-old argument on the relative merits of analog and digital computation, it has been said that the true future for scientific computation involves the union of the equipments by means of an analog-digital converting device. In this period prior to the digital computer with fractional-microsecond arithmetic commands and memory accesses, it appears that for many problems such a union is necessary. Or, from another point of view, considerable machine time savings can be realized from such a union. The Digital Computing Center and the Analog Computing Center of The Ramo-Wooldridge Corporation have cooperatively arranged for the design and construction of a general purpose analog-digital conversion device, the system point of view of which will be discussed here especially in relation to the digital computer. The conversion equipment will be obtained on a contract with the Epsco Company of Boston, Massachusetts, and is scheduled for delivery in October 1956. The conversion and control techniques are the result of Epsco developments with the system organization and specifications the responsibility of The Ramo-Wooldridge Corporation. The equipment will tie in the Univac Scientific Model 1103A digital computer with a large analog computer installation consisting mostly of Electronic Associates Corporation equipment. The 1103A computer is a large-scale system consisting of 4096 words of magnetic core memory, Uniservo magnetic tapes (up to 10 in number) for input-output and auxiliary storage, and a magnetic drum of 16,384 word capacity. Computing speeds for the equipment are approximately 50 microseconds for addition and 250 microseconds for multiplication (times include memory accesses). The analog equipment consists of 300 operational amplifiers including 108 integrating amplifiers, 16 resolvers, 24 servo multipliers, function generating equipment, and a number of x-y and six-channel recorders. The equipment has 3 operating consoles and can be used on as many as 6 independent problems at one time. The conversion equipment will have sufficient speed and accuracy so that analog results will not be degraded in the translation from analog to digital form. There will be 15 conversion channels each way — that is, 15 analog-to-digital channels and 15 digital-to-analog channels. The authors believe this system, with the analog-to-digital tie-in effected, will be one of the most powerful computation facilities available.