Did you know?
The TI-99/4A was the first ever home computer to host a 16 bit processor?



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!

Texas Instruments  TI-99/4a. Released 1981.

The TI-99/4A 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. Lovely.


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 Wars').


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!

John 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.

Access 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 Editor Assembler.

Easily 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...

Starfield 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.


Yours truly :-)

Welcome to my little corner of 99er.net. It's warm and dry in here, so hunker down and make yourself comfortable!


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 Instruments TI-99/4A.


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 Darwin.


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 Writers Toolkit.


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 TI-99/4A 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 on Alpiner, 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:

Editor Assembler

  • 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.



TI Base

  • 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 the TI:

  • TI-Basic (built into the console)
  • TI Extended Basic, much more powerful, supplied as a plug in cartridge
  • Logo - A language designed to teach children how to program computers
  • 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. Nice.
  • C - a subset, or 'compact' version of C. I learned C with this! Clint Pulley rocks!


Horizon Ramdisk

  • 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