#### Back to index | # Info for ti99_4

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

Known Issues:
Requires full keyboard emulation. At startup, full keyboard emulation mode is
enabled by default. Whilst in full keyboard emulation mode, some key
associated functionality may be disabled (like the ESC key for EXIT).
The keyboard emulation mode is toggled using the scroll_lock key.
A TI-99/4 is not a TI-99/4a. Most programs are compatible with both /4 and
/4a, but some programs require a /4a.
The BwG disk controller has display bug which causes it to change the character
definitions for no appearent reason, but, out of this, it seems to work fine.
If this is an issue, you may revert to the TI disk controller.

Usage:
See the sysinfo entry for the ti-99/4a driver.
The only extra feature is the IR remote handsets. This feature was abandoned
by TI at the last minute, but the support was seemingly not deleted from the
ti99/4 ROMs until the release of the ti99/4a. This feature is disabled by
default because some programs are incompatible with it, but it can be enabled
by setting the IR remote handsets dip-switch on and resetting the emulator
(press F3 in so-called partial keyboard emulation mode to reset the emulator).
A few programs can use the improved joysticks (TI-Invaders seems to be one of
them).

History and Trivia:
The TI99/4 Home Computer was designed and built by Texas Instruments. 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" cartridges, 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 microcontroller, 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).

Generated on Wed Jul 16 01:11:08 2003