CDC 160 series - Misplaced Pages

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CDC 160
CDC 160-A with close-up of control panel
Developer	Seymour Cray
Manufacturer	Control Data Corporation
Release date	1960 (1960)
Introductory price	$100,000 equivalent to $1,029,921 in 2023
Units shipped	400
Storage	4096 words of magnetic core
Power	115 V, 12 A
Dimensions	29 by 61+1⁄2 by 30 inches (740 mm × 1,560 mm × 760 mm)
Mass	810 lb (370 kg)
Successor	CDC 6000 series

The CDC 160 series was a series of minicomputers built by Control Data Corporation. The CDC 160 and CDC 160-A were 12-bit minicomputers built from 1960 to 1965; the CDC 160G was a 13-bit minicomputer, with an extended version of the CDC 160-A instruction set, and a compatibility mode in which it did not use the 13th bit. The 160 was designed by Seymour Cray - reportedly over a long three-day weekend. It fit into the desk where its operator sat.

The 160 architecture uses ones' complement arithmetic with end-around carry.

NCR joint-marketed the 160-A under its own name for several years in the 1960s.

Overview

A publishing company that purchased a CDC 160-A described it as "a single user machine with no batch processing capability. Programmers and/or users would go to the computer room, sit at the console, load the paper tape bootstrap and start up a program."

The CDC 160-A was a simple piece of hardware, and yet provided a variety of features which were scaled-down capabilities found only on larger systems. It was therefore an ideal platform for introducing neophyte programmers to the sophisticated concepts of low-level input/output (I/O) and interrupt systems.

All 160 systems had a paper-tape reader, and a punch, and most had an IBM Electric typewriter modified to act as a computer terminal. Memory on the 160 was 4096 12-bit words. The CPU had a 12-bit ones' complement accumulator but no multiply or divide. There was a full complement of instructions and several addressing modes. Indirect addressing was almost as good as index registers. The instruction set supported both relative (to the current P register) and absolute. The original instruction set did not have a subroutine call instruction and could only address one bank of memory.

In the 160-A model, a "return jump" and a memory bank-switch instruction was added. Return-jump allowed simple subroutine calls and bank switching allowed other 4K banks of memory to be addressed, albeit clumsily, up to a total of 32,768 words. The extra memory was expensive and had to be contained in a separate box as large as the 160 itself. The 160-A model could also accept a multiply/divide unit, which was another large and expensive peripheral box.

In the 160 and 160-A, the memory cycle time was 6.4 microseconds. An add took two cycles. The average instruction took 15 microseconds, for a processing rate of 67,000 instructions per second.

The 160G model extended the registers and memory words to 13 bits; in G mode, all 13 bits were used, while in A mode, only the lower 12 bits were used, for binary compatibility with the 160-A. The 160G added some instructions, including built-in multiply and divide instructions, and some additional addressing modes.

Low-level I/O allowed control of devices, interfacing for determining device status, and for reading and writing data as either single bytes, or as blocks. I/O could be completed to a register, or to memory, or via a direct memory access (DMA) channel. The distinction between these I/O types was that regular I/O would 'hang' the CPU until the I/O operation completed, but DMA I/O allowed the CPU to proceed with instruction execution concurrently with the data transfer. The interrupt system was purely based on IO, meaning that all interrupts were generated externally. Interrupts were introduced to neophytes as being the alert mechanism by which a program could be informed that a previously initiated DMA I/O operation was completed.

Application areas

Real-time applications
Off-line data conversion
Scientific data processing
Commercial data processing
Data acquisition and reduction
Engineering problem solving
Communications and telemetering systems
Control Data's Satellite Computer System

Peripherals

163 or 164 Magnetic tape systems
161 Typewriter unit
1610 Card read and punch system
1612 Line printer
165 Plotter
166 Buffered line printer
167 Card reader
168 Arithmetic unit
169 Auxiliary memory unit
350 Paper tape reader
Model BRPE-11 Teletype paper punch tape punch
603 Magnetic tape transport

Successors

The 160 architecture was modified to become the basis of the peripheral processors (PPs) in the CDC 6000 series mainframe computers and its successors. Large parts of the 160 instruction set were unchanged in the peripheral processors. However, there were changes to incorporate the 6000 data channel programming, and control of the central processor. In the early days of the 6000s, almost the entire operating system ran in the PPs. This left the central processor unencumbered by operating system demands and available for user programs.

References

^ 160 Computer Programming Manual (PDF). Control Data Corporation. 1960. Retrieved March 28, 2013.
^ Control Data 160-A Computer Programming Manual (PDF). Control Data Corporation. March 1963. Retrieved March 28, 2013.
^ Control Data 160G Programming Reference Manual (PDF). Control Data Corporation. May 11, 1965. Retrieved March 28, 2013.
^ Lawrence Liddiard (May 1986). "Seymour Cray's Machines (Part 2)" (PDF). The CDC 160, rumored to have been designed over a weekend by Cray, was CDC's first $60,000 desk (not desktop) computer that became the prototype I/O processor for the peripheral processors surrounding the CDC 6600 and 7600.
"A Programmer's Reference Manual for the CDC-160" by Douglas W. Jones
Flamm, Kenneth (1988). Creating the computer: government, industry, and high technology. Brookings Institution Press. p. 118. ISBN 0815728506.
Peter Clark (July 1982). "DEC TIMESHARING (1965)". The DEC Professional. p. 34.
Control Data 160 Typewriter Unit (PDF). Control Data Corporation. December 1962. Retrieved March 28, 2013.
Control Data 160 Computer (PDF). Control Data Corporation. Retrieved March 28, 2013.
Control Data 160-A Computer (PDF). Control Data Corporation. November 1962. Retrieved March 28, 2013.
"Control Data 160G Computer System" (PDF). Control Data Corporation. Retrieved March 28, 2013.
^ "Control Data 160 Computer" (PDF). August 1961. Retrieved November 26, 2017.