Elliott NRDC 401 Mk I Mainframe Computer

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.

Here you find 5 models, 5 with images and 2 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Elliott Brothers Ltd.; Elliott Brothers (London) Ltd.; London, Marconi-Elliott (Microelectronics) Ltd.; Glenrothes