TI 990 architecture / was Re: TI-99/4A Floppies
chaosotter76 at gmail.com
Mon Oct 8 14:55:45 CDT 2007
On 10/3/07, Allison <ajp166 at bellatlantic.net> wrote:
> There are really three 99/4 home computers:
> original with chiclet keys the 99/4
> the second and most common with a really nice keyboard 99/4a
> the white console version that is really the same thing with
> a few board level cost reductions. (still 99/4A on the back)
There's a caveat associated with the white/beige console version, actually:
Most (all?) of them have an additional lockout chip to prevent the use of
third-party cartridges -- in particular, the Atarisoft games that came in
the black wedge-shaped cases.
More than any of the technical considerations that have been mentioned,
that's probably the biggest reason why TI's home computer division flopped:
their outright hostility to third-party development. Commodore laid all the
internals bare, even to the point of including schematics in the
programmer's reference, whereas you STILL can't find a decent technical
reference for TI's GPL interpreter.
It is a pity that they laid out the memory the way they did, with the
standard 16KB as ported video memory, because the assembly is really fun to
work with. I've installed a CompactFlash sidecar with 32KB memory expansion
on my old 99/4A, and that's made it into a fun computer again.
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