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Rockwell 920

Rockwell 920


Distinctive features: Used an early 4-bit microprocessor, the Rockwell PPS-4 (Parallel Processing System).  Is "designed to be easily programmable in a business office or scientific laboratory".  Programs saved on magnetic cards.

Capabilities: 4 function, limited scientific, programmable, magnetic card reader.

Designed to be easily programmable in a business office or scientific laboratory, with conditional jumps, symbolic addressing, memory indirect addressing, subroutine nesting to 4 levels, and simple debugging and editing.
Each magnetic card can store 256 program steps on each side, and can also be used for storing data.  Rockwell had an extensive library of programs available on magnetic cards that they could supply.

Display: 14 digits, amber gas discharge and printer.

Technolgy: Uses a very early microprocessor system[1], the 4-bit Rockwell PPS-4[2], based on the 10660 cpu.  The Large Scale Integration (LSI) ICs are here date coded from 1974 to mid 1975, and comprise the Rockwell[3]:

Size: 297 mm x 425 mm x 155 mm (12" x 17" x 6.25"), 8.25 Kg (18.25 lbs).

Rockwell International
Business Equipment Division/Sunnyvale California.
Assembled in Mexico, US, and Foreign Parts.
[Distributed in the UK. by Sumlock Anita Ltd.]

Significance: Uses the early Rockwell PPS-4 microprocessor, with printer and magnetic-card reader.  This results in a large calculator with a lot of integrated circuits, which were required at this time for the memories, the card reader, and the printer.
The Rockwell PPS-4 system was also used in industrial and consumer products such as electronic toys and games[4].

See also the Busicom 141-PF which uses the early Intel 4004 microprocessor.

Rockwell 920 card reader

Rockwell 920 with a magnetic card about to be read.

Rockwell 920 with cover removed

Rockwell 920 with cover removed.

Inside Rockwell 920

With the cover and keyboard removed, showing most of the integrated circuits of the Rockwell PPS-4 microprocessor system.  The display is at top left, and the magnetic card reader is at top right.

Further information about Rockwell can be found in the Calculator Companies section.


  1. "Four-bit microprocessor cycles instructions in 5 μs", Electronic Design, March 1, 1973, p94.
  2. "Rockwell PPS-4", 'AntiqueTech' website.
  3. "Data Sheet - Parallel Processing System (PPS-4) Microcomputer", Microelectronic Device Division, Rockwell International Corporation, 1973, p2.
  4. "PPS-4 - Rockwell International", 'WickiChip' website.

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Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.