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#### Texas Instruments TI-99/4 Home Computer

Known Issues:
This TI99/4 driver is preliminary and could not be tested.

History and Trivia:
The TI99/4 Home Computer was designed and built by Texas Instrument. About
200 prototypes were built in 1978, it was first shown in June 1979, and TI
started shipping it in October 1979. It was replaced with TI99/4a in the
summer of 1981. It was first sold in US, then was available in Europe in
early 1981.
This computer was easy to use. It displayed nice color graphics, and
played sound. It was highly expandable, too. One expansion enabled the
computer to speak. Programs were generally on cartridges. TI, which always
tried to keep the control of program production, put an emphasis on games,
education, and home utilities (home finance, etc.). Incidentally, it was
the first 16-bit home computer.
The general architecture was odd. The computer had only 256 bytes of CPU
RAM, the remaining 16kb of RAM were attached to the video processor. It
had been designed to use some slow "GROM" cartridge, written in an
interpreted language, "GPL".
Due to these poor designing and programming choices, the computer was slow.
The keyboard was uneasy to use, and there was serious bugs in ROMs. Also,
it wasn't until november 1980 that TI could build a TV modulator to attach
the computer to a TV instead of a monitor. Worse, the computer was awfully
expensive for a home computer (more than $1000 with the monitor, more than
dozen thousand units were sold.
The design of TI99/4 caused many headaches to TI engineers. It was first
designed as a console, then an inexpensive home computer (which explains
its slowness and kludgy design), then a hybrid (with remote I/R joysticks
and keypads - which were abandoned at the last minute - and a cartridge
port). It was intended to use a TI-designed processor, tms9985, but the
processor was never actually produced, so engineers had to use a
software-compatible, high-end (in 1979) tms9900 with tons of glue logic.
Note that the processor software design was remarkably weird (no stack, no
on-chip data register).

Wanted:
If you have a TI99/4 ROM image, or if you know how the extra system GROM
maps in the memory space, please mail me at pytheas@club-internet.fr

created on Tue Jan 01 12:56:01 2002