page_title: IBM 1620
section_title: Peripherals
hierarchical_section_title: IBM 1620 / Peripherals
caption_attribution_description: w:IBM 1627 drum plotter at InfoAge Vintage Computer Museum. Pen assembly is missing.
context_page_description: The IBM 1620 was announced by IBM on October 21, 1959, and marketed as an inexpensive "scientific computer". After a total production of about two thousand machines, it was withdrawn on November 19, 1970. Modified versions of the 1620 were used as the CPU of the IBM 1710 and IBM 1720 Industrial Process Control Systems.
  Being variable-word-length decimal, as opposed to fixed-word-length pure binary, made it an especially attractive first computer to learn on – and hundreds of thousands of students had their first experiences with a computer on the IBM 1620.
  Core memory cycle times were 20 microseconds for the Model I, 10 microseconds for the Model II. The Model II was introduced in 1962.
context_section_description: Available peripherals were:
  IBM 1621 –  Paper tape reader
  IBM 1622 –  Punch card reader/punch
  IBM 1624 –  Paper tape punch (sat inside the 1621 on a shelf)
  IBM 1626 –  Plotter controller
  IBM 1627 –  Plotter
  IBM 1311 –  Disk drive: Model 3 master drive controlling up to 3–Model 2 slave drives.
  IBM 1443 –  Printer, flying type bar
  IBM 1405 –  Disk Drive available as RPQ (request price quotation)
  The standard "output" mechanism for a program was to punch cards, which was faster than using the typewriter.  These punched cards were then fed through an IBM 407 mechanical calculator which could be programmed to print two cards, thus being able to use the additional print columns available on the 407.  All output was synchronous, and the processor paused while the I/O device produced the output, so the typewriter output could completely dominate program running time.
  A faster output option, the IBM 1443 printer was introduced May 6, 1963, and its 150–600 lines/minute capability was available for use with either model of the 1620.
  It could print 120 or 144 columns.  The character width was fixed, so it was the paper size that changed; the printer printed 10 characters to the inch, so a printer could print a maximum of 12 inches or 14.4 inches of text.  In addition, the printer had a buffer, so the I/O delay for the processor was reduced.  However, the print instruction would block if the line had not completed.
caption: IBM 1627 drum plotter
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