====== Texas Instruments TI-99/8 Computer (1983) ======
===== Usage =====
The TI-99/8 looks a lot like the /4(a). Press any key to begin, then press A for the built-in BASIC interpreter, B to set speed, C, D, etc, for any inserted cartridge. Set speed does not apply to the built-in BASIC interpreter, which will always run at full speed. The default speed is "B TI-99/4A speed": you must run set speed to select any other speed.
Though the level of compatibility with the /4a is high, you may not access extensions provided by an inserted cartridge from /8 BASIC, whether they are packaged as a CALL or as a DSR.
== Keyboard ==
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.
===== Known Issues =====
There is no known dump of TI-99/8 ROMs. I have reassembled the source code of the TI-99/8 ROMs, which has enabled me to reconstruct the core of the operating system. Unfortunately, several optional but important parts of the system (HexBus, P-System, Speech ROMs, and named subroutines in BASIC) are missing.
Speech that sounds fine on a /4(a) with the optional speech synthesizer may sound garbled on a /8 with its integrated speech synthesizer.This is because the /4a and the /8 do not use the same speech chip (TMS0285 vs. TMS5200C).On an actual /8, this only affects programs that use custom speech; under emulation, this currently affects programs that use pre-defined speech as well, because the /8 speech ROMs have not been dumped and we resort to using the incompatible /4(a) speech ROMs instead.
Mapper-level Read protect, Write protect and Execute protect are not emulated. Hard reset and P-code GROMs are not emulated either.
===== History and Trivia =====
When TI released the TI-99/4 in 1979, they announced that a bigger, more professional version of this machine would follow: the TI-99/7. After several delays, the TI-99/7 project was abandoned, and in 1981 TI started a similar project with upgraded specs: the TI-99/8 (code-named Armadillo).
The project was nearing completion, with a prototype series in production, when TI terminated the TI-99 series in October 1983. As a consequence, the TI-99/8 was never released, although several prototypes ended in private hands.
The TI-99/8 is similar to, yet different from, the TI-99/4(a). Mostly, it looks like a super TI-99/4(a): it has a faster CPU, a better keyboard, and several features that were optional on the /4(a) (speech synthesizer, HexBus controller and UCSD P-system). However, it includes several features that have no equivalent on the /4a: its memory mapper enables it to address 64kBytes of RAM simultaneously, to support more than 15MBytes of RAM, and to implement partial memory protection; also, its ROMs are a lot improved compared to the /4(a) ROMs: they support machine language programs much better, they implement several extra system calls for graphics, and they support I/O buffer in CPU RAM.
Generated on Sun Jul 19 10:17:28 2009