Geoff Macdonald's Computer Museum
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Scientific programmable Calculator

  • Released 1975
  • 9V Alkaline battery or mains adaptor
  • 9 digit 7-segment green vacuum fluorescent display
  • 5 digit precision
  • Reverse polish data entry
  • Sine, cosine, arc-tangent, antilog, log, reciprocal, square and square root

This is a very basic programmable calculator with many shortcomings.  Although there is a 9 digit display, the precision is limited to 5 digits because 3 are reserved for the exponent.  There is no "power of" function.  The reverse polish entry is limited by a two level stack, which is destroyed whenever a scientific function is used.  The programming model is wasteful, for example constants require a start and end quote.  Constants in programs must be integers.


ZX81

  • Released 1981
  • CPU Z80 at 3.58MHz
  • RAM 1k (expandable to 32k)
  • ROM 8k
  • Text 32x15 (black & white)
  • Graphics 64x44 (black & white)
  • Tape storage

    Successor to the ZX-80, this computer replaced much of the discrete logic with a ULA. Further cost reductions were the membrane keyboard and a TV interface directly driven by the CPU (and shared with the tape interface, which produced some nice patterns when loading and saving). A dedicated electrostatic printer was available which printed on "silver toilet roll". This machine was really the start of the "home computer revolution".

Spectrum 48

  • Released 1982

  • CPU Z80A at 3.5MHz

  • RAM 48k

  • ROM 16k

  • Text 32x24 (16 colours)

  • Graphics 256x192 (16 colours)

  • 1 channel sound

  • Tape and Microdrive

    Very popular machine with a large software base. Several variations were made, a 16k Spectrum 16, Spectrum+ with a better case and keyboard (similar to the QL) and Spectrum+128 with 128k RAM. The rights were sold to Amstrad who continued the range.


QL

  • Released 1984

  • CPU 68008 at 7.5MHz

  • RAM 128k

  • ROM 32k

  • Text 85x25

  • Graphics 512x256 (4 colours), 256x256 (8 colours)

  • Two integral Microdrives

    The first 16bit(ish) home computer. This machine was released a year before the Atari ST and Commodore Amiga, but initial production problems, use of microdrives instead of floppy discs and the slower 68008 CPU stopped it from becoming as popular.

 
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Copyright (C) 1999-2002 by Geoff Macdonald

Last updated 03/09/2002