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Chapter 35

PILOT, the NBS multicomputer system1

A. L. Leiner / W A. Notz / J. L. Smith / A. Weinberger

Summary PILOT, the new NBS system, possesses both powerful external control capabilities and versatile internal processing capabilities. It contains three independently operating computers. The primary and secondary computers each utilize only 16 basic types of instructions, thus providing a simple code structure; but because so many variations of the formats are possible, a wide variety of computing, data-processing, and information-retrieval operations can be performed with these instructions. The secondary computer is specially adapted for performing so-called "red-tape" operations, and both the secondary and the primary computers, acting co-operatively, can carry out special complex sorting or search operations. The third computer in the system, called the format controller, is specially adapted for performing editing, inspecting, and format modifying operations. The system is equipped to transfer information concurrently along several input-output trunks, though only two are planned for the near future. Using two such trunks, it is possible to maintain two continuous streams of data simultaneously flowing between any two external units and the internal memory, without interrupting the data-processing program. The system can operate with a wide variety of input-output devices, both digital and analog, either proximate or remotely located. The external control capabilities of the system enable the machine to supervise this wide family of external devices and, on an unscheduled basis, to interrupt or redirect its overall program automatically, in order to assist or manage them.

At the National Bureau of Standards (NBS) a new large-scale digital system has been designed for carrying out a wide range of experimental investigations that are of special importance to the Government. The system can be utilized for investigating new or stringent applications of these general types: (1) data-processing applications, in which the system can be used for performing accounting and information-retrieval operations for management purposes; (2) mathematical applications, in which the system can be used for performing mathematical calculations for scientific purposes, including scientific data-reduction; (3) control applications, in which the system can be used for performing real-time control and simulation operations, in conjunction with analog computer facilities or in conjunction with other instrument installations, remotely located if necessary; and (4) network applications, in which the system can be used in conjunction with other digital computer facilities, forming an interconnected communication network in which all the machines can work together collaboratively on large-scale problems that are beyond the reach of any single machine.

Because the system was designed for such varied uses (ranging from automatic search and interpretation of Patent Office records to real-time scheduling and control of commercial aircraft traffic), the system is characterized by a variety of features not ordinarily associated with a single installation, namely: a high computation rate, highly flexible control facilities for communicating with the outside world, and a wide repertoire of internal processing formats. The system contains three independently programmed computers, each of which is specially adapted for performing certain classes of operations that frequently occur in large-scale data-processing applications. These computers intercommunicate in a way that permits all three of them to work together concurrently on a common problem. The system thus provides a working model of an integrated multicomputer network.

System organization

Exclusive of data-storage and peripheral equipment, the central processing and control units of the over-all system contain approximately 7,000 vacuum tubes and 165,000 solid-state diodes. The basic component for these units is a modified version of the one megacycle package used in the NBS DYSEAC, which in turn was evolved from the hardware used in NBS Electronic Automatic Computer (SEAC). As a result of a more effective logical design and faster memory, however, the new NBS system will run more than 100 times faster than SEAC on programs involving only fixed-point operations; for programs involving floating-point manipulations, the advantage exceeds 1,000. The arithmetic speed of the new system derives in a large part from connecting a novel type of parallel adder to a diode-capacitor memory capable of providing one random access per microsecond.

The system contains seven major blocks, which are indicated in Fig. 1, namely: (1) the primary computer, in the lower center

1Proc. EJCC, 71-75 (1958).


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