CDC 1700

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The CDC 1700 was a 16-bit word minicomputer, manufactured by the Control Data Corporation with deliveries beginning in May 1966. [1]

Minicomputer class of smaller computers

A minicomputer, or colloquially mini, is a class of smaller computers that was developed in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000, with an input-output device such as a teleprinter and at least four thousand words of memory, that is capable of running programs in a higher level language, such as Fortran or BASIC. The class formed a distinct group with its own software architectures and operating systems. Minis were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation and record keeping. Many were sold indirectly to original equipment manufacturers (OEMs) for final end use application. During the two decade lifetime of the minicomputer class (1965–1985), almost 100 companies formed and only a half dozen remained.

Control Data Corporation defunct supercomputer firm

Control Data Corporation (CDC) was a mainframe and supercomputer firm. CDC was one of the nine major United States computer companies through most of the 1960s; the others were IBM, Burroughs Corporation, DEC, NCR, General Electric, Honeywell, RCA, and UNIVAC. CDC was well-known and highly regarded throughout the industry at the time. For most of the 1960s, Seymour Cray worked at CDC and developed a series of machines that were the fastest computers in the world by far, until Cray left the company to found Cray Research (CRI) in the 1970s. After several years of losses in the early 1980s, in 1988 CDC started to leave the computer manufacturing business and sell the related parts of the company, a process that was completed in 1992 with the creation of Control Data Systems, Inc. The remaining businesses of CDC currently operate as Ceridian.


Over the years there were several versions. The original 1700 was constructed using air-cooled CDC 6600-like cordwood logic modules and core memory, although later models used different technology. The final models, called Cyber-18, added four general-purpose registers and a number of instructions to support a time-sharing operating system. [2]

CDC 6600 computer

The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the IBM 7030 Stretch, by a factor of three. With performance of up to three megaFLOPS, the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600.

In computing, time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking at the same time.

System nameProcessorMinimum RAMMaximum RAMCycle time
170017044 KW32 KW1.1 μs
1714171412 KW64 KW1.1 μs
SC170017744 KW32 KW1.5 μs
System 1717844 KW64 KW0.9 or 0.6 μs
CYBER 18MP1716 KW128 KW0.75 μs


The 1700 used ones' complement arithmetic and an ASCII-based character set, and supported memory write protection on an individual word basis. It had one general-purpose register and two indexing registers (one of which was implemented as a dedicated memory location). The instruction set was fairly simple and supported seven storage addressing modes, including multilevel (chained) indirect addressing.

The ones' complement of a binary number is defined as the value obtained by inverting all the bits in the binary representation of the number. The ones' complement of the number then behaves like the negative of the original number in some arithmetic operations. To within a constant, the ones' complement behaves like the negative of the original number with binary addition. However, unlike two's complement, these numbers have not seen widespread use because of issues such as the offset of −1, that negating zero results in a distinct negative zero bit pattern, less simplicity with arithmetic borrowing, etc.

ASCII American computer character encoding

ASCII, abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.

In computer architecture, a processor register is a quickly accessible location available to a computer's central processing unit (CPU). Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. Registers are typically addressed by mechanisms other than main memory, but may in some cases be assigned a memory address e.g. DEC PDP-10, ICT 1900.

Although described as a 16-bit system, the basic core storage memory was 4,096 18 bit words, each comprising

Magnetic-core memory predominant form of random-access computer memory for 20 years between about 1955 and 1975

Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core.


Available peripherals included teletypewriters, paper tape readers/punches, punched card readers/punches, line printers, magnetic tape drives, magnetic drums, fixed and removable magnetic disk drives, display terminals, communications controllers, Digigraphic display units, timers, etc. These interfaced to the processor using unbuffered interrupt-driven "A/Q" channels or buffered Direct Storage Access channels.

Teleprinter device for transmitting messages in written form by electrical signals

A teleprinter is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initially they were used in telegraphy, which developed in the late 1830s and 1840s as the first use of electrical engineering. The machines were adapted to provide a user interface to early mainframe computers and minicomputers, sending typed data to the computer and printing the response. Some models could also be used to create punched tape for data storage and to read back such tape for local printing or transmission.

Punched tape form of data storage

Punched tape or perforated paper tape is a form of data storage, consisting of a long strip of paper in which holes are punched to store data. Now effectively obsolete, it was widely used during much of the twentieth century for teleprinter communication, for input to computers of the 1950s and 1960s, and later as a storage medium for minicomputers and CNC machine tools.

Punched card recording medium

A punched card or punch card is a piece of stiff paper that can be used to contain digital data represented by the presence or absence of holes in predefined positions. Digital data can be used for data processing applications or, in earlier examples, used to directly control automated machinery.


The main operating systems for the 1700 were the Utility System, which usually took the form of several punched paper tapes (resident monitor plus utilities), a similar Operating System for larger configurations (often including punched cards and magnetic tape), and the Mass Storage Operating System (MSOS) for disk-based systems.

An assembler and a Fortran compiler were available. [1] Pascal was also available, via a cross compiler on a CDC 6000 series host. The Cyber 18 series, exploiting the extended instruction set, ran a disk-based OS, the Interactive Terminal Oriented System (ITOS). This system supported Fortran, Cobol, and UCSD Pascal. ITOS was a foreground/background system with multiple users connected via serial CRT terminals; user tasks ran in the background while the operating system itself ran in the foreground.

Market acceptance

The 1700 series found use as communications concentrators, Digigraphics workstations, remote batch job entry stations, and industrial process controllers. [3] One application, running the AUTRAN program, controlled water and wastewater treatment plants for many years. Another was used as Maintenance and Diagnostic SubSystem (M&DSS) for the AN/FPQ-16 Perimeter Acquisition Radar Attack Characterization System (PARCS), located at Cavalier Air Force Station (CAFS) in North Dakota; this CDC 1700 is still being used as of this writing (2016).

Washington, DC used a Control Data 1700 in vote-tallying. [4] CDC's 1700 was also used by Ticketron as central servers for their wagering systems and ticketing services. [5]


In mid-2016, John Forecast added a CDC 1700 simulator to the SIMH package. [6]


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IBM System/3 IBM minicomputer

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CDC 3000 series

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CDC 6000 series family of mainframe computers

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CDC 160 series

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NOS (software)

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  1. 1 2 3 "Control Data 1700 Computer System - Computer Reference Manual" (PDF). Control Data Corporation. September 17, 1965.
  2. CDC Cyber 18 Processor With MOS Memory, Macro Level System Description (PDF). CDC. 1977.
  3. RE Hohmeyer (1968). "CDC 1700 FORTRAN for Process Control" (PDF).
  4. "It was decided to change the program of the CDC 1700. Changing the program without a public test May violate the spirit if not the letter of the D.C. Rules. Roy G. Saltman (1978). Effective Use of Computing Technology in Vote-tallying.
  5. "... at the heart of the TRS system for well over a decade was the Control Data 1700. ... The CDC 1700 appears with Bill Norris in a photo that ran alongside ..." Budnick, Dean; Baron, ?Josh (2012). Ticket Masters: The Rise of the Concert Industry. ISBN   978-1101580554.
  6. "CDC 1700 emulator added to SIMH".

Philips Technical Review, Volume 36, 1976, No., p.162 ff. Computer-aided design by Peter Blume: An early application of the CDC 1700 Digigraphic: shows in Fig. 4 a complete schematic of the computer configuration and in Fig. 5 a picture of the Digigraphic display Abstract:.... Work has been in progress at the Philips Laboratories in Hamburg since 1973 ... on an integrated computer system in which parts are completely detailed in a dialogue between the designer and a computer via an "interactive display" ...

The mentioned display is the display of the CDC 1700 Digigraphic. Fig. 4 Figure caption: The CDC 1700 Digigraphic computer system for the graphic processing of data. The interactive display is connected to the CD 1704 central processor via a control unit with a "picture store"; the computer itself has the usual mass stores and peripheral equipment. Information from the computer store can be displayed on the screen of the picture tube and can be altered or added to by using a light pen and keyboards connected to the interactive display. This means that very fast input of both alphanumeric and graphic information is possible, while the input can be verified immediately on the screen.