IBM 650 | 1954

 

The IBM 650 Magnetic Drum Data-Processing Machine: A Pioneering Computer

The IBM 650, introduced in the mid-1950s, was a groundbreaking digital computer, notable for being the first mass-produced computer in the world. Nearly 2,000 units were manufactured by IBM, with the last one rolling off the production line in 1962. The IBM 650 was not only significant for its production numbers but also for being the first computer to generate a meaningful profit for its manufacturer. Its initial installation took place on December 8, 1954, at the John Hancock Mutual Life Insurance Company in Boston.

Market Position

The IBM 650 was marketed primarily to businesses, scientific institutions, and engineering firms as a more affordable and slower alternative to the IBM 701 and IBM 702. It also appealed to users transitioning from punched card machines like the IBM 604. Its affordability and programming simplicity made it a versatile tool, paving the way for various applications, including academic use where it became a fundamental part of computer programming education.

Technical Specifications

The IBM 650 was a two-address, bi-quinary coded decimal computer with memory stored on a rotating magnetic drum. Its clock frequency was 125 kHz, enabling it to perform addition or subtraction in approximately 1.63 milliseconds and multiplication in 12.96 milliseconds. The average instruction execution time was around 27.6 milliseconds, translating to roughly 40 instructions per second.

Memory and Storage

Main memory options included configurations of 1,000, 2,000, or 4,000 words, with each word comprising ten bi-quinary coded decimal digits. This setup allowed for significant flexibility in data handling. The drum could rotate at 12,500 RPM, with an average access time of about 2.5 milliseconds.

Hardware Components

The basic IBM 650 system included:

  • IBM 650 Console Unit: housed the magnetic drum and arithmetic device.
  • IBM 655 Power Unit
  • Card Reader/Punch Unit: either the IBM 533 or 537, which handled data input and output.

Optional components enhanced its functionality, such as disk storage units, magnetic tape controllers, and additional memory features.

Instruction Set

The instruction set of the IBM 650 comprised a two-digit operation code followed by a four-digit data address and the next instruction's address. The base machine supported 44 operation codes, expandable to 97 with optional features like floating-point arithmetic and index registers. Unique capabilities included the Table Lookup (TLU) instruction, which efficiently compared data across memory.

Legacy

The IBM 650's impact on computing education and business applications was profound, with Donald Knuth famously dedicating his series "The Art of Computer Programming" to it. Despite its eventual obsolescence and the withdrawal of support in 1969, the IBM 650 remains a significant milestone in the history of computing, illustrating the evolution from mechanical calculators to electronic data processing.


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