West Coast Contributions to the Development of the General-Purpose Computer: Building Maddida and the Founding of Computer Research Corporation

by the Author of Paper Given Before The Association for Computing Machinery Conference at Rutgers University, New Brunswick, New Jersey March 28-29, 1950 “Maddida” — General Theory By Floyd G. Steele Two devices are normally used to simulate the mathematical process of integration—the analogy integrator and the numerical accumulator. It is possible by employing a numerical technique to produce a device having the logical characteristics of an analogy integrator and the accuracy and repeatability characteristics of a numerical device. A set of digital integrators may be inter-coupled in the manner natural to the ordinary Differential Analyzer to solve ordinary differential equations or sets thereof, either linear or non-linear. Further, numerical integrators may be stored in a memory in a manner which yields simplicity of utilization and communication. A magnetic drum digital differential analyzer called Maddida has been built and put into operation. It was designed to have 44 digital integrators, each having an accuracy of 1 part in a million. Fifty-six tubes were required, not including power supply and readout. It is apparent that a machine having about 132 numerical integrators can be built with a total of about 100 tubes. The digital differential analyzer appears to have the advantage of fewer tubes, economy, speed, accuracy, and possibly greater reliability over the normal analogue devices which solve ordinary differential equations. In computation, it has the advantage of easy coding, accuracy, and considerable economy. In control, it will be found to intervene between sensory devices and effectors more directly than the ordinary numerical machine and to require fewer components than standard analogy devices. It should prove of use in those control problems which require either extensive facility or high accuracy. It is hoped that this type of machine can serve both to enlarge the scope of automatic control and to provide individual computation. Acknowledgment is made to Donald Eckdahl and Dick Sprague for general logical contributions on the digital differential analyzer and to Donald Eckdahl, William Collison, Harold Sarkissian, and Dick Sprague for specific logical contributions on the machine Maddida. Valuable mathematic assistance has been rendered by Dr. Irving Reed. Abstract by the Author of Paper Given Before The Association for Computing Machinery Conference at Rutgers University, New Brunswick, New Jersey March 28-29, 1950 “Maddida” — Design Features By Donald E. Eckdahl Maddida—Magnetic Drum Digital Differential Analyzer—is an electronic digital computer which integrates differential equations directly, as do the analogue Differential Analyzers. Integration is accomplished by operating on pairs of numbers by an additive transfer process. A register n digits in length containing a number “y” is added into a register “R” of equal length upon each occurrence of an input pulse “dx.” All carries from register “R” are used as incremental outputs “dz.” The number in “y” can be increased or decreased by an input “dy.” The result is that dz = ydx/Bn where “B” is the base of the number system used. A paper by the originator of this type of machine, Floyd G. Steele, at this conference, covers fully the theory of such integrators and a number of different methods of possible realization. One machine, which will be discussed by Richard E. Sprague at some later date, utilizes complete flip-flop storage.1 Maddida stores the registers mentioned on a magnetic drum and operates on each pair of numbers serially. A pair of numbers is called an integrator. A total of 22 such integrators are stored on the drum. The control and arithmetic center sees only one digit of one integrator at a time. The number system is binary and the additive transfer process is accomplished by serial binary addition. A one-word register on the drum stores and routes the outputs of the integrators to inputs of other integrators. Each integrator contains a code section which defines the manner of connection with other integrators in the machine. The memory stores 22 pairs of 48 digit words on two channels. A one-word register is provided on a third channel by closer spacing of the heads. A clock or timing source is permanently recorded on the drum for synchronization and constant delay adjustment of the memory. The drum is used as a delay memory in constant re-circulation. A non-return to zero system is used, the memory output controlling a flip-flop on two grids. At some later date, a paper by Harold H. Sarkissian will cover fully the details of this memory.1 The machine contains 60 vacuum tubes including those used in the memory. Additional tubes are present in the four regulated power supplies. One thousand germanium diodes are used for logical operations and for clamping and coupling on the flip-flops. Abstracts of Papers Presented to the ACM Conference at Rutgers University