• Year
  • 1953 ?
  • Category
  • Signal Processing and Computing
  • Radiomuseum.org ID
  • 363127

 Technical Specifications

  • Wave bands
  • - without
  • Power type and voltage
  • Alternating Current supply (AC)
  • Loudspeaker
  • - - No sound reproduction output.
  • Material
  • Various materials
  • from Radiomuseum.org
  • Model: Elliott NRDC 401 Mk I Mainframe Computer - Elliott Brothers Ltd.; Elliott
  • Shape
  • Rack
  • Notes
  • Elliott NRDC 401 Mk I Mainframe Computer

    • Year Introduced: 1953
    • System Type: Serial binary mainframe computer using 2’s complement fixed-point arithmetic.
    • Word Length: 32 bits per word (plus 2 gap bits), supporting integer arithmetic and logical operations.
    • Arithmetic Units: Includes two accumulators, a multiplier register, and general-purpose registers for flexible computing.

    Performance:

    • Addition and subtraction are executed in approximately 200 microseconds.
    • Multiplication takes between 7 to 10 milliseconds, depending on operand sign.

    Memory:

    • Primary memory is a magnetic drum (fixed-head disk) with initially 1,024 words (8 tracks × 128 words).
    • Designed for expansion up to 23 tracks, allowing roughly 2,944 words maximum capacity.
    • Supplemented by fast internal nickel delay line registers for quick data access.

    Instruction Format:

    • 32-bit instructions with two addresses — one for the operand and one for the next instruction.
    • Support for approximately 28 primary machine operations, including arithmetic, logic, shifts, conditional branches, input/output, and manual control.

    Input/Output Devices:

    • Photoelectric 5-level paper tape reader operating at 40 characters per second.
    • Electric typewriter output at 10 characters per second used for program results and debugging.
    • Later hardware expansions incorporated tape punch and card reader capabilities.

    Physical Construction:

    • Built using vacuum tubes (around 500 valves), housed in large cabinetry measuring roughly 13 feet long by 2 feet deep and 7.5 feet high.
    • An internal air-cooling system maintains operational temperature.
    • Designed with modular plug-in valve circuits for ease of maintenance and repair.

    Control and Programming:

    • Manual addressing and programming were required due to sequential memory access.
    • Programs were written directly in machine code, with libraries developed for common mathematical routines.
    • Manual control features included handswitch inputs and output feedback via CRT displays and speakers.

    Typical Applications:

    • Mainly scientific and statistical calculations, including operations research and data analysis.
    • Emphasis on reliability and maintainability for continuous use in research environments.
  • Mentioned in
  • -- Collector info (Sammler) (Technical Details of the Elliott 400 Series Computers, Alex Reid.)
  • Author
  • Model page created by Gary Cowans. See "Data change" for further contributors.

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