microWAT Microcomputer

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microWAT Microcomputer


computer hardware: microcomputer


Historical context:

Early microprocessor-based computers (microcomputers) presented a cost-effective and low-maintenance alternative to high-performance minicomputers that dominated the computer scene of the 1970s. Their utilization was confined largely to applications that did not require the full processing power of the minis. Microcomputers also presented a unique opportunity to expand and enrich academic computing programs and environments.

A 1979 study conducted at the University of Waterloo (UW) on possible use of microcomputers for academic applications concluded that "many of the jobs run on computers at Waterloo could be done using the computational capacity possessed by microcomputers." [1] However, "none of the inexpensive, mass-manufactured microcomputers had the appropriate hardware to operate our planned software, mainly because the memory was not large enough, and because there was insufficient flexibility, particularly with respect to input/output." [1] The study set in motion two microcomputer development projects at the
Computer Systems Group (CSG) of UW -- the microWAT and the SuperPET.

The microWAT was designed jointly by CSG and Jerry Krist of Northern Digital Ltd. of Waterloo. The computer was demonstrated in December 1980 and subsequently manufactured by Northern Digital. The microWAT was a small CPU unit that required a separate keyboard, display, and external storage to form a computer system. At UW, MicroWATs used Volker-Craig video display terminals and Commodore IEEE disk drives. Several microWATs were installed inside "dumb" display terminals converting them into versatile desktop computers that could operate with diskette drives, printers, plotters, and could be networked with other systems such as the IBM Series/1 minicomputers operating at UW.

The computer was built around the Motorola 6809 microprocessor and all its hardware was deposited on several printed circuit boards including the CPU, I/O, ROM, and RAM boards. An additional small ROM card sealed from tampering (referred to as the "key" card or the "chocolate bar") was a software security device containing a key required to access software written at UW including micro BASIC, Pascal, FORTRAN, COBOL and APL. According to former Northern Digital employee Heinz Wolter

"The most interesting thing in that whole system was that Wes Graham (of Watfor fortran compiler fame) had written a copyrighted poem (Haiku) that was an unencrypted key required to run the software."

The microWATs were used, among other places, at UW for academic teaching and research. The introduction of the IBM PC in August 1981 and the subsequent rapid growth of IBM PC-compatible computer market put an end to the microWAT and SuperPET programs.

microWAT technical specifications:
  • CPU -- Motorola 6809, 8-bit
  • RAM -- three memory cards, 32Kb each
  • ROM -- 60Kb
  • ports -- two RS-232 compatible serial ports (implemented using MOS Technology 6551 Asynchronous Communications Interface Adapter),
  • a single parallel port (implemented using the MOS Technology 6522 Versatile Interface Adapter)

microWAT software:
  • monitor
  • micro BASIC, Pascal, FORTRAN, COBOL and APL languages
The museum has a microWAT computer with a CSG "key" card.


[1] D.D. Cowan and J.W. Graham, Waterloo Microcomputer Systems for the 1980's, Proceedings of the ACM '82, pp. 13–17 (1982).

[2] R.L. Hughson, Alternations in the oxygen deficit-oxygen debt relationship with beta-adrenergic receptor blockade in man", J. Physiol. 349, pp. 375-387 (1984).


Developed by the University of Waterloo, Manufactured by Northern Digital Ltd.






Ontario, Canada, 1980-1983[?]

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Developed by the University of Waterloo, Manufactured by Northern Digital Ltd., “microWAT Microcomputer,” York University Computer Museum Canada, accessed May 27, 2023, https://museum.eecs.yorku.ca/items/show/47.

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