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TI 99/4A

  • Released 1981

  • CPU TMS9900 at 3MHz

  • RAM 16k (expandable to 1MB)

  • ROM 26k

  • Text 32x24 (16 colour)

  • Graphics 256x192 (16 colour)

  • 1 channel sound

  • Tape storage

    This is an improved TI99/4, which was originally released in 1979, with additional graphic modes, a better keyboard and smaller ROMs. It never became popular for several reasons:
    It was slow: The TMS9900 is a 16bit processor, so this machine should have been the fastest available. However, only 8k of ROM and 256 BYTES of RAM are on the 16 bit bus. Everything else is on a multiplexed 8 bit bus. Plus, the three interrupts are all on the same line, so the software has to poll to determine an interrupt source. This is because the machine was originally designed to use a TMS9985, which has an external 8bit bus and a single interrupt line. The TMS9985 was never produced commercially because of technical problems.
    Very little software was produced for it: TI patented an interpreted "Graphics Programming Language" GPL. Operating system functions were only available to GPL programs. To control the production of cartriges, information on GPL was only available to companies who had signed a non-disclosure agreement with TI. When Atari independantly released cartriges, TI modified the ROMs to only accept GPL programs. This had the effect of preventing software companies from releasing programs for the machine.

 
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Copyright (C) 1999-2002 by Geoff Macdonald

Last updated 29/08/2002