Did you know?
The TI-99/4A was the first ever home computer to host a 16
Did you know?
The 99/4A had four types of memory - ROM, RAM, GROM, and VDP. ROM
and RAM was accessible to the processor as normal, whilst VDP memory
was only 'visible' by going thorugh the graphics processor chip.
GROM as a custom made type of auto-address incrementing rom that
contained code to be hosted on a plug in cartridge!
was the second machine from Texas Instruments that perhaps
should have been part of a trilogy. It's predecessor,
the TI/99-4, was poorly received by the market. Poor
performance, no high resolution graphics, and a terrible
keyboard drove the customers away in droves. Enter stage
left the new TI-99/4 - with a A, with a 'real' keyboard,
high resolution graphics, and better expansion options.
This time, TI (for a while) struck gold. The (American)
public loved it, and it flew from the shelves. A combination
of snazzy marketing by TI (selling the machine in regular
stores instead of geeky computer stores) and a TV campaign
led by such famous stars as XXXX meant the machine had
high market visibility. It's TI sponsored educational
software, developed by companies such as Plato meant
it was the obvious choice in schools and homes alike.
But there was trouble ahead...
Despite TI's dominance, other competitors were approaching,
with equally capable hardware, and, more importantly,
more, (and cheaper) available software. TI adopted a
fatal stance with regard to software development - rather
than encouraging third party developers to develop for
the machine, and provide assistance, they actively discouraged
it, even threatening court action and modifying the
machines design to stop third-party plug in cartridges
from working. No problem. The software houses of the
day, where the real innovation was happening, simply
wrote for other computers such as the VIC 20 and Atari
range of machines, leaving the TI lagging way way behind.
TI's answer to this was to drop the price of the machine,
eventually to as low as $99, (from around $1000 at it's
launch) - the fatal blow that was to lead to TI's complete
withdrawal from the home computer market, never to return,
even to the point of canceling all projects relating
to the 4A's big brother, the very impressive TI-99/8.
Soon, every TI sold lost TI money, while it's competitors,
(notably Commodore) were sitting rather comfortably
(although there were many casualties of the 'Home Computer
Today, there is still a thriving TI community, with
new software being written, and, amazingly, new hardware
being developed. If you want to run USB devices on your
1982 TI, you can. If you want to run hard disks, you
can. If you want megabytes of RAM, you can!
Conway's Game Of Life - The mathematical
simulation as invented by British mathematician John
Conway, is available in downloads section, written in
100% TMS9900 Assembly, runs with Editor Assembler.
16MB memory expansion in Win994A - Win994a
offers 16MB of extra memory over the original 32k that
came on an expanded TI. Check out my memory tester in
the downloads section, which shows you how to access
the full 16MB. Written in 100% machine code, runs with
design 16x16 sprites with program written in XB
- I wanted a good sprite designer for the 4a for a game
I plan to develop, but all the ones I tried in XB were
seriously slow and rather limiting. This version, in
XB, lets you work with six 16x16 sprites at a time,
rotate them, scroll them, invert them, save them, and
reload them for later editing, and is at least twice
as fast as the other ones I tried...
Simulation - My first machine code program
on the TI since 1991, when I released The
Game Writers Toolkit through Abbots Software. If
you are interested in game writing on the old 4A, and
want a starfield, then check out this code, which does
it without using sprites - nice, pixel by pixel scrolling.
Welcome to my little corner of 99er.net.
It's warm and dry in here, so hunker down and make
This site is my little tribute to the computer that
got me started in the computer industry, and the reason
I make a living working with the computers - the Texas
I have been getting back into the 4A for late, using
mainly the fabulous Win994a emulator by Cory Burr,
available for download
on 99er.net (see
the dedicated forums
for lots of Q/A's about Win994a).
Because of Win994a, I have been writing some code once
again, and so I thought I would make the code I write available
to all via these pages. All downloads on this site are to
be considered public domain, unless stated otherwise.
So, a little about me: My name is Mark Wills, I am 35 year
old (at the time of writing!) programmer/engineer and started
programming computers at the age of 11, way back in 1982.
I live in Shropshire, England, born in Shrewsbury,
the birth place of Charles
I run my own company,
in conjunction with my business partner, and together, we
work all over the world (mainly eastern/asian countries)
on oil & gas fields, getting all the control systems
to work, which keeps us rather busy!
In 1982, instead of going home after school for something
to eat, I would go to our local Co op store on Lancaster
Road in Shrewsbury and spend all evening writing simple
little programs on the computers there - my favourite one
being the TI-99/4A, because of the awesome Parsec and Alpiner
cartridges that the sales staff would let me play (presumably
it was good for sales!) My father would come and pull me
out of the store at about 7 o'clock, and apologise to the
staff there, who would always say "Oh, it's alright,
he's no trouble, and he's helping to sell the computers!"...
Unknown to me, he later ordered a 4A from the store, and
it was my Christmas present on Christmas day, 1982!
I soon got through TI-Basic, and started buying cassettes
from Stainless Software (the famous Stephen
Shaw) in Cheshire, however, the lack of affordable software
in the UK meant the steady demise of the TI in the UK, and
by 1983, it was all over.
I returned to the TI for a while in 1989/1991 and released
a few programs, and was Vice Chairman of the TI-99/4A
UK user group, which, still to this day publishes a
quarterly magazine. The most notable work from me at that
time was The Game
One day, out of boredom probably, I typed in TI-99/4A into
Google and was amazed
at all the hits, In just a few minutes I had joined the
email list at yahoo groups, re-joined the TI
User Group UK after 14 years, and enjoying a darned
good game of Parsec...
Excellent stuff :-) By the time I had gotten to Everest
I had re-connected with my youth, and I was hooked... Forget
washing the car, this is IT!
And so, here I am... As I write more code for the old 4A,
mainly to satisfy my own desires, needs, or curiosities,
i'll post them here on this site to download. Please feel
free to help yourself. All code will be released as Win994a
disks, unless otherwise stated.
My Favourite TI Programs:
Favourite TI Hardware:
- The essential bit of software for the TI-99/4A - Using
this cartridge and disk software combination you can write your
own assembly language programs in 9900 assembly language. The
9900 instruction set is lovely, as elegant as many more modern
processors such as the Motorola 68000.
Millers Graphics Explorer
If you want to write assembly on the TI, you need this program.
It's a virtual 9900 running a 9900! Using this program you can
produce disassemblies of your code, single step, select breakpoints
in CPU, VDP or GROM memory areas, and much more! Simply ingenious
bit of programming from Craig Miller of Millers Graphics.
- A really great database system for the 4A. Very similar to DBase
- those of you old enough to remember DBase will remember that
you designed your own screens, and database schema, then, rather
than use SQL as we do these days, you wrote script files, essentially
programs, that processed your data. Excellent stuff, and worked
very on the memory contrained computers of the day,
UCSD P-Code Card
This was a virtual processor card, in hardware form! Using this
card and it associated software, one can develop PASCAL code on
the TI. There are plenty of languages available for tinkerers on
- TI-Basic (built into the console)
- TI Extended Basic, much more powerful, supplied as a plug in
- Logo - A language designed to teach children how to program
- Forth - Always looked like gobbledy-gook to me, but, if you
are into your stack based, reverse-polish notation languages,
this is the one for you. It's damned fast!
- FORTRAN - a faithful representation of the ANSI FORTRAN 77 standard.
- C - a subset, or 'compact' version of C. I learned C with this!
Clint Pulley rocks!
- This was a really neat bit of kit. The ram disk sat in the Peripheral
Expansion Box and pretended to be a disk drive, but was in fact,
a giant battery backed ram-card. Even after the system was powered
down, the contents of the 'drive' were not lost. I had a 512K
wire wrapped (!) version, built by Colin Hinton, an ex TI-UK ermployee.
Site designed by Mark Wills using Macromedia's
Dreamweaver MX ©2006