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 Seymour Roger Cray (September 28, 1925 – October 5, 1996
) was an American

It fit into the desk where its operator sat. The 160 architecture uses

ones' complement The ones' complement of a binary number is the value obtained by inverting all the bits in the binary representation of the number (swapping 0s and 1s). The name "ones' complement" (''note this is possessive of the plural "ones", not of a sin ...

arithmetic with

end-around carry In computing, signed number representations are required to encode negative numbers in binary number systems. In mathematics, negative numbers in any base are represented by prefixing them with a minus sign ("−"). However, in RAM or CPU regis ...

. 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 In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...

(I/O) and

interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...

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 A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and ...

. Memory on the 160 was 4096 12-bit words. The CPU had a 12-bit

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 Bank switching is a technique used in computer design to increase the amount of usable memory beyond the amount directly addressable by the processor instructions. It can be used to configure a system differently at different times; for example ...

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 live 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 Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is ...

(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 The CDC 6000 series is a discontinued family of mainframe computers manufactured by Control Data Corporation in the 1960s. It consisted of the CDC 6200, CDC 6300, CDC 6400, CDC 6500, CDC 6600 and CDC 6700 computers, which were all extremely rapid ...

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 An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

ran in the PPs. This left the central processor unencumbered by operating system demands and available for user programs.

References

External links

Control Data 160-A Overview

Computer History Museum- CDC 160A
{{Control Data Corporation 160-A Transistorized computers 12-bit computers