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. 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.

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.

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.[1]

System name Processor Minimum RAM Maximum RAM Cycle time
1700 1704 4 KW 32 KW 1.1 μs
1714 1714 12 KW 64 KW 1.1 μs
SC1700 1774 4 KW 32 KW 1.5 μs
System 17 1784 4 KW 64 KW 0.9 or 0.6 μs
CYBER 18 MP17 16 KW 128 KW 0.75 μs

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. A Fortran compiler was available. 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.

The 1700 series found use as communications concentrators, Digigraphics workstations, remote batch job entry stations, and industrial process controllers. 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). The system was also used by Ticketron as central servers for their wagering systems and ticketing services.


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


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