back to article 81's 99 in 17: Still a lotta love for the TI‑99/4A – TI's forgotten classic

The retro computing and gaming scene is seeing no shortage of interest these days. Old fans and curious millennials are flocking to take nostalgia trips on the popular consoles of the 1980s. While the likes of the ubiquitous NES, Atari 2600 and Apple II have all received attention, there are other, lesser-known machines that …

  1. Andrew Moore

    My first home computer...

    I still have a lot of fond memories, even though it ran like a bit of a dog and was useless without the Expanded Basic module.

    1. chasil

      Re: My first home computer...

      It was mine too.

      The software was terrible. The BASIC lacked peek() and poke(), so getting down to the metal with the bare-bones model was not possible.

      The CPU in the base unit had a TINY amount of RAM (less than 1k) - all the memory was tied to the TMS9918(a) video chip. This is where a user's BASIC program was stored, and the CPU would converse with the VDP to run the user's program. Wow, that was a terrible idea.

      You could get a "Mini Memory" cartridge with a watch battery that gave you 4k of CPU ram, but it was laughable for development in assembler. There was a full Editor/Assembler cartridge, but you had to have a memory expansion and disk system before you could run it.

      This machine required a very large pile of peripherals before it gave you any glimpse of how it actually worked.

      When I read about the BBC Micro and the wonderful interpreter it bundled, I'm convinced that TI should never write an interpreter of any sort ever again.

      1. PT

        Re: My first home computer...

        Well, they were in a bit of a bind regarding PEEK and POKE, because the 9900 didn't use addresses as we know them. It was unique in microcomputer history in designating A0 as the MOST SIGNIFICANT address line (And D0 as the MSB on the data bus). This was presumably because it didn't have a least significant address (a real A0), having only a 15 bit address bus. Presumably there was a way to read or write a single byte, but I can't remember now. TI inexplicably started marking their EPROMs backward the same way - very confusing - and there must have been many bills of materials with a note saying "NO TI" whenever an EPROM was called out. I know it was on all my BOMs. It took them a couple of years to get the message.

  2. Deltics
    Thumb Up

    I had me one of those

    A lot of my extended family worked at TI in Bedford (UK) and when they EOL'd the '99 staff were able to pick one up for chump change, so we got one through an uncle still working there. This was my upgrade from a ZX81.

    An amazing bit of kit really, for the time and thanks to it's market failure a lot of add-ons could be picked up for pocket money. Cartridges were great for a quick bit of gaming at a time when for someone with a Speccy or a 64, you had to factor in the loading time, from tape. The '99 could load from tape as well, and some games still required that (Scott Adam's Adventures being a prime example). But those cartridges were great, and could add capabilities to the base machine to enable more advanced games (I seem to remember Parsec did something like that).

    I also had a lot of fun with the speech synthesizer add-on module and a graphics tablet (!!) whilst the Extended BASIC cartridge provided a decent place to learn programming, compared to the rather idiosyncratic BASIC that was on-board otherwise.

    e.g. Extended BASIC gave us advanced features such as sprites and .... PRINT AT.. Without that, printing strings to the screen was a rather tortuous affair involving GOSUB routines and FOR NEXT loops calling HCHAR() (don't ask).

    And then there were the UDG's (User Defined Graphics for people who didn't grow up in the 80's - you might also need to look up "sprite" :) ). I learned hex as a result of memorising the bit patterns associated with the strings necessary to define 8x8 UDG blocks, e.g. your classic solid 8x8 circle/disc: 3C7EFFFFFFFF7E3C

    Eventually I upgraded to an Amiga A500. :)

    Aaaah, happy days.

    1. Anonymous Coward
      Anonymous Coward

      Re: I had me one of those

      The Commodore models supported cartridges as well - just they were usually more expensive than the (often pirated...) software on tape, and thereby far less common. I should still have a pirate adventure game cartridge somewhere. They were inserted in the rear expansion port.

  3. Anonymous Coward
    Anonymous Coward

    While we're on the subject of TI...

    What in creation is up with the TI-84 calculator? It's one of the ugliest, slowest, most retro pieces of computing power I've ever seen...yet all the kids textbooks use it and TI seem to have a lock on the market. As a Euro transplant to the US it blows my mind that people still make kids use them.

    1. DNTP

      Re: While we're on the subject of TI...

      I have the same TI-89 that I (got my parents to) bought when I was in high school. Even for 1999 it had a slow, outdated processor; today it's absolutely stone-age compared to a modern smartphone.

      Anyway, this overpriced clunky monopolized chunk of ugly black plastic, dim puke-grey screen and obscurely confusing interface, got me through two years of high school, 4 years of college, and 10 years of molecular genetics and it still works just as well right now where it is a permanent feature of my desk.

      That's why people buy TI graphing calculators, aside from all the superficially horrible overpriced features they are in fact extremely useful general purpose mathematical tools.

      1. kain preacher

        Re: While we're on the subject of TI...

        In the US people buy TI calculators be cause they are on the approved listed for SAT and ACT. They also flood schools with cheap TI calcs

        1. Grunchy Silver badge

          Re: While we're on the subject of TI...

          There were two "camps" being TI-85 vs HP-48gx. You either understood & appreciated RPN and used the HP, or you hated it and used the TI.

          I couldn't afford neither, and furthermore, both were prohibited from any exams because of the potential to sneak in exam data in their memories & graphical displays. One guy put in all the steel phase charts, for example...

          So I picked up a Sharp EL-531Q and that was it. Cheapest they had at campus bookstore.

          Works to this day, except I have to remove the caseback with a screwdriver in order to change the battery.

          I did get an Atari Portfolio, which was cool because it utilized DOS commands. However it was sluggish & primitive and my landlord stole it, I think.

          I'm getting me a Psion Gemini off Indiegogo! well, maybe :)

      2. Pedigree-Pete

        Re: While we're on the subject of TI...

        My 1st "scientific" calc was a TI too. Had logs, cosigns, tangents etc. Not that we could use them in exams tho'. Had to use bloody slide rules and tables. '77-80! Stone age. PP

    2. Elf

      Re: While we're on the subject of TI...

      I have asked myself this question quite reacently, actually. I tripped over an Android App that *emulated* the TI-84...On My Way to an app that I'd used before, quite superrior in all ways. I was frankly baffled. A few days later, an eerie feeling crept over me in a coffee-house (not Starbucks) by the University in Seattle ... nearly all of the students has this calculator (did you know it comes in colors and stuff?...and you can get armored cases for it like handsets, which, frankly seems both expensive and counter-productive).

      I looked it up and it seems to have *declined* in cost from when I was but a College Lad, it is still a sack of crap.

      To the TI/99 though; I taught myself to program on that bad-boy (Extended BASIC Cart). While certainly not one of my favorite machines of all time, I *will* always love it.

      1. Anonymous Coward
        Anonymous Coward

        Re: While we're on the subject of TI...

        Obligatory xkcd reference:

  4. JLV

    How about also including RPN calculators like the HP-48C on the poll list? The only RPN left is the HP-12 which is a financial calculator, nowhere as geeky :(

    My first "program" ever was a probability calculator for it, to give you the odds of various Advanced Squad Leader hit results - i.e. how likely is that Russian 4-4-7 to chew up my squad, given its -1 NCO and my open terrain move mod of -2?

    1. Anonymous Coward
      Anonymous Coward

      > How about also including RPN calculators like the HP-48C on the poll list? The only RPN left is the HP-12 which is a financial calculator, nowhere as geeky :(

      You need to visit

      If by "HP-48C" in your comment you meant HP-41C then they have an HP-41C clone (although the landscape format takes a bit of getting used to!). If you actually meant HP-48SX then wait 6 - 8 months - they have it in the pipeline but there's a 42S clone to come out first.

      1. Simon Rockman

        The HP x3 phone has a 12C app on it.

  5. Anonymous Coward
    Anonymous Coward

    YA Memory Comparison

    RAM and Storage comparisons are not really amusing any more, but I couldn't help thinking that my current PC has more RAM than all the Ti99/4s that shipped, combined.

    1. Anonymous Coward
      Anonymous Coward

      Re: YA Memory Comparison

      True. I think I like it for the apparent value that lower storage brings you over the generations of consumer hardware. If you were around when a 20 Mega Byte disk drive was as big as they came, and that only represented about 20 floppy discs, and it cost many hundreds of dollars, you can appreciate getting a nice WD 3TB drive for about US$100 that much more! The 20MB drive still works, but it makes an awful noise, and really my floppy archive has so much more in it. The oldest drive I can remember the price of was a Jasmine 100MB internal drive for a Mac SE with the special "third bay" mounting rack was about US$300. Nowadays that can buy 6 Raspberry Pi boards and have change left for SD cards and power cords. Value!!1!

      Good on the TI-99 folks! Keeping old kit running is better than it being in a museum. Old hardware never dies, unless it dies, so take care of it!

  6. Christian Berger

    In the early 1990s I got it along a ZX80

    The TI was essentially useless with the stock BASIC, it barely allowed you to do primitive text mode graphics. I also compared the speed to my ZX80 and it was many times slower.

    Infact if you displayed the whole character set and redefinied characters, you could see the BASIC interpreter moving its data away from the space used by unused user defined characters.It had something like 128 words of RAM accessible to the processor, while its 16 kilobytes were all dedicated to the graphics chip... so every access had to go through the graphics chip. To make it even slower, the BASIC interpreter was itself interpreted.

    Some accessories removed some of the problems. For example you could give the CPU some actual RAM apparently, but those things were completely unobtainable back then.

    1. Paul Shirley

      Re: In the early 1990s I got it along a ZX80

      At the time it looked underpowered and the addons weren't easily available. Smacks of a deliberate policy to drive sales of extra hardware needed to bring it up to spec. No big surprise the more complete as shipped C64 wiped it out.

  7. arcadeshopper


    Thanks for the great article. There are many of the TI add-ons, cartridges and mods on my website including that great Megademo on cartridge! I'll also be linking to your article in my blog there.

  8. TRT


    Just... what a machine!

  9. psychonaut


    id forgotten about this. my mate had one. great bit of kit! loved the cartridges.

    mind you i had a bbc b i think at that stage.

  10. Steve Todd

    Interesting machine, but hamstrung by TI marketing

    Yes, it had a 16 bit CPU, but they only gave it 256 bytes of 16 bit memory. All the rest was a nasty 8->16 bit multiplexed cludge. TI marketing didn't want it to compete with their lucrative mini computer market, so they deliberately made sure it couldn't.

    1. This post has been deleted by its author

      1. Steve Todd

        Re: Interesting machine, but hamstrung by TI marketing

        Sorry AC, your nerd mode failed. It had a full TMS9900 @3MHz. TI had intended to use the TMS9995, but had problems with it. They did use the 9995 in the TI 99/2 and TI 99/8, but they never got beyond the prototype stage.

        BTW, both chips were NMOS, so had the same hideous power requirements. The 9900 (and I presume the 9995) needed a complex 4 phase clock, which might be where you got the 12MHz number from.

        1. This post has been deleted by its author

        2. grumpyoldeyore

          Re: Interesting machine, but hamstrung by TI marketing

          @Steve Todd - I never knew it went back to the 9900 - all the early technical press referred to it using the 9995. The 9995 was designed to be cheaper by having a lower pin count - hence the multiplexed bus. I'm pretty sure that the 4 phase clock went as well. We used the 9900 where I worked, and looked at the 9995 as a possible cost saving but decided that the re-design was not worth it, I've also a vague recollection that the hardware integer divide was removed from the instruction set which was the USP for the 9900 in the first place. (memory may be clouded by the passage of 35+ years).

        3. ForthIsNotDead

          Re: Interesting machine, but hamstrung by TI marketing

          The TMS9995 did not exist then the TI-99/4 was designed. The 9995 was designed by a student at TI Bedford (UK) who went on to design the successful TMS34010 and TMS34020 graphics chips.

    2. Ken Hagan Gold badge

      Re: Interesting machine, but hamstrung by TI marketing

      "TI marketing didn't want it to compete with their lucrative mini computer market, so they deliberately made sure it couldn't."

      Hmm. That sounds familiar...

      Is this a common pattern? The established vendor doesn't want the new technology to eat into their existing markets, so they are eaten (whole) for breakfast by upstart competitors who don't mind offering a product that eats into that market. (Moral: cannibalism is good because at least it is you doing the eating.)

  11. SHIFT838


    The article was a great read. The TI community is one of the best I have been involved in and seems to have a lot of new development for hardware and software.

    My favorite cartridge today is the FlashRom99.

    And thank you for the mention in the article!

    Chris Schneider


    FuSiON BBS :

    telnet to :

    port # 9640

  12. ForthIsNotDead


    I have a Forth system on a cartridge for the 4A which is still under active development! In 2017!

    Check out for a home-grown British Forth system for the 4A!

  13. Captain DaFt

    And for the curious

    A TI emulator for Windows

    And Modern TI software!

    All free! (But a donation to the programmer wouldn't hurt! ☺)

  14. Canadian eh?

    TI was backwards

    Speaking of kludges; was TI's idea of bit-order. In TI land, bits were numbered from 1 to 16, with the Least significant bit being bit 16 (for those that might not have been around during those years, today we call that bit 0).

    I built an add-on board for one of my TRS-80 Model 1s that used the same TMS 9918 graphics controller found in said TI99/4A. What was really interesting about that graphics controller was that it used DRAM, when everyone else at the time was using much more expensive SRAM.

    It was quite the brain warp to adjust to "their" way of thinking, but luckily their world view on bit ordering didn't hold in the end.

    1. tom dial Silver badge

      Re: TI was backwards

      While starting with bit 1 rather than bit 0 is a bit quirky, bit 0 (or 1) often or usually is the most significant bit on word-oriented processors like the TMS9900, Motorola 68000, and IBM 360/370/390.

    2. Kristian Walsh Silver badge

      Re: TI was backwards

      In low-level communications, bits are numbered in transmission order, and bytes are transmitted from most to least significant bits (as far as I can tell, only by convention). Put those two things together and the MSB is bit 0, because it is first one that gets put out onto the wire or broadcast into the aether. (This convention of transmitting bits from most to least significant is also why "network" byte order is Big-Endian).

      CPU people went with LSB =#0 on the grounds that it made more mathematical sense - it matches the power-of-two value of that bit position.

      1. Ken Hagan Gold badge

        Re: TI was backwards

        "bytes are transmitted from most to least significant bits (as far as I can tell, only by convention)"

        Possibly because if the same value were transmitted as text then it would naturally be transmitted big-endian and *that* is (allegedly) because the Europeans learned their arithmetic from the Arabs (who designed the system the other way but write right-to-left) but failed to swap the "byte-order" when copying the text books.

        1. hmv

          Re: TI was backwards

          Just to be picky, we stole the _digits_ not arithmetic from the Arabs; I'd imagine doing arithmetic in Roman numerals would drive anyone to theft!

    3. grumpyoldeyore

      Re: TI was backwards

      From memory, that actually depended on which version of which data sheet you read. A new circuit was being built at the first company I worked for, using aTI9900. At board bring up, the data bus was fount to be "the wrong way round". The PCB design team had a V1 data sheet with D0 as the MSB and created the library shape thus. The HW designer had a V2 data sheet with D0 as the LSB. I also recall that the programming manual had A16 as the MSB and a long philosophical discussion about A0 which didn't actually come out of the chip, but was replaced by a "byte selector".

  15. Alex Vincent

    I was three years old when I woke my dad up to save a program I'd written on the TI-99/4A to a cassette tape. I had no idea it was a rare machine or even unpopular. It was just fun, especially with Logo and BASIC.

  16. Ed 13

    Splendid machines

    I recall the Extended Basic was something of a must, but ate a couple of K of precious RAM. So you were caught between a rock and a hard place as your program wouldn't work in the standard mode, and wouldn't fit in the extended mode!

    Parsec is still one of my favourite games.

    They had one at the Cambridge Museum of Computing when I was there. I thoroughly recommend the place, they have lots of kit turned on and you can just play with it.

    1. w1bble

      Re: Splendid machines

      my 1st puta was a TI-99/4A .. I played parsec for months before finding out I could slow down the speed for refuelling :)

      I loved the machine as it was the first thing I took apart, put back together and it still worked.

      My 2nd machine was a BBC B, which shows my age !

  17. Anonymous Coward
    Anonymous Coward

    I worked on 990/10 and /12 at TI

    I worked on 990/10 and /12 at TI back then .

    HP screwed that company up too by buying the "Explorer " Lisp platform that essentially ended Ti's mini-computer era.

  18. Kev99 Silver badge

    I bought a TI99/4A (which was actually their second microcomputer). My wife would get upset because I'd hijack our tv and plug the unit into it. I finally got a splitter and left it connected all the time. I wrote a simple BASIC program for it that drove people nuts. It first asked a bit of a tough question, No matter how you answered, the program responded you were wrong and should try again. I had it programmed so that each time it's response was ruder and nastier. Finally after the fifth try the program responded the user was too dumb to use a computer and would shut down the machine.

  19. Unicornpiss

    I love this old stuff..

    ..and the history of computing, especially microcomputers. While my first computer was a Commodore PET, I found a TI 99/4 in a thrift store some years back with a few cartridges. It was a little battered but sported the original box and accessories and worked perfectly. I played with it for a while and ended up ebaying it for $100. It was purchased by a guy across the country that taught grade schoolers and wanted to use it to teach them BASIC programming. I have little doubt that it's still running.

    I still have that original PET too, along with an 8050 disk drive and printer. (and it all still works, though I haven't tried the printer in a long time) That and a few ancient 8-bit coin-op arcade games that are increasingly hard to keep running with entropy doing its thing.

  20. tullio

    Wings for the mind

    The TI99/4A had been chosen by the Istituto Tecnologie Didattiche del National Research Council to introduce primary school children to programming in BASIC and especially LOGO. An Italian version of TI LOGO was created by Giovanni Lariccia with its Manual. Mondadori Publishing House printed an Italian version of Horacio C.Reggini "Alas para la mente" and "Artificial Intelligence An Introductory course" by the University of Edinburgh Press.Franco Muzzio Editore . published "A scuola con il Texas Instruments TI99/4A" by Sergio Borsani. Then Texas Instruments retired the machine and the whole project, presented by Milan State University professor Gianni degli Antoni, fell flat.

    I have used the TI99/4A to introduce my kids, male and female, to programming but they used it mostly to play games, some of which I still have. I used it to simulate a moon landing.

  21. Anonymous Coward
    Anonymous Coward

    Happy to see the love

    One big development for the 99/4A which is cross-platform is Matthew's F18A, an FPGA replacement for the TMS-9918A, variants of which wound up in numerous other systems, like the MSX, ColecoVision, and more†. It gives the system SVGA output, new screen modes, multi-color sprites, has an option to eliminate the five-sprite-per-line limitation, and provides a fast implementation of the 9900 in the GPU (yes, the 99/4A can now be a multi-processor computer.)

    There are a lot more expansions enabling better programming and gaming, and better portability, really showing the 99/4A as a capable peer of the better-known systems of its era, like the Commodore 64 and Atari 8-bits. A number of folks in the AtariAge forum‡ have Lotharek floppy emulators in the full-size PEB, or use the scaled-down nanoPEB which puts 32k, floppy emulation with a CF card, and an RS-232 interface on a small side-car module. Competent emulation like Classic99 and MAME can provide your gaming fix without the real machine as well as a super-fast development platform††.

    Games abound including a monthly game contest where other members pony up TI-related prizes to the winners, loads of programming options like gcc, TurboForth, file-based fbForth, many options for assembly, a fantastic Extended BASIC compiler. Too much to really detail, you just have to see for yourself.



    †† and

  22. allthecoolshortnamesweretaken

    Re: desktop setup of TI-99/4A fan Omega (pic)

    Now that is a joystick. And the trackball isn't bad either...

    The TI-99/4A... I remember it well. Not a bad piece of kit, but never really got popular over here. In fact, the other nerds thought of you as an oddball if you had one of those. What really killed it was the lack of games availiable. Let's face it, we all told our parents that we needed that computer thingy "for school", and it had to have a proper keyboard for typing all that homework. Once the floppy disc drive for the C64 was availiabe (and could be paid for with the money from a summer job) every other system was dead in the water.

  23. Outsider


    OK, so it's not a "real" computer..... but I cut my teenage programming teeth on a TI59.

    It taught me how to think logically and optimise the use of limited resources. The amazing thing was it's portability..... I regularly used it in the field saving hours of tedious paper calculation, with corresponding increase in available pub time. It took until the early 2000's for my industry to routinely use a handheld device that could do what the TI59 could do in 1980.

    In my youth I didn't understand why they didn't catch on...... but then again my university dept had just bought a load of Imperial Office Master mechanical calculators... the power of the smartly besuited salesman on the greyhaired senior manager never dims.

    1. Milo Tsukroff
      Thumb Up

      Re: TI59

      The TI-59 ... ahh, THAT was a calculator! I used one in my college years. Still have it. Although I use a Windows-based TI-59 emulator when I need a quick calculation or two.

      Later on I bought a TI-99/4A and I was hooked. I LOVED that thing. Still have a number of them gathering dust in the garage.

      One comment though: The TI-99/4A was one of only two REAL COMPUTERS to be released in the 1970's-1980's microcomputer boom. If you learned to program it in Assembly, as I did, it had a "floating workspace" which coexisted in the single linear memory space, which along with programs and data, also used memory locations for I/O. All addressed in the same manner as linear memory. This architecture is "classic" computer architecture. Only Texas Instruments and DEC released microcomputers like this.

      All other micros used microprocessors, which have to move data from linear memory, to on-board registers, and then back out. This ham-strings their operation and makes them much, much slower. That was why the TI-99/4A ran acceptably fast enough, even with a horrendously slow clock rate. Of course, the sheer speed of microprocessors was so blindingly fast by the mid-1980's that it didn't matter about all the time needed to swap data in and out of on-board registers. Current speeds are so fast that nobody cares.

      But "back in the day" it sure was nice to see that the TI-99/4A was using assembly language statements that could have come straight from mainframe computers. When the IBM PC first came out in 1981, a game released with it was Adventure. If memory serves me, way deep in the Wizard's cave are copies of LWPI magazine. That instruction, Load Workspace Pointer Immediate, is used in linear memory addressing. I could use it in TI-99/4A assembly. It DOES NOT exist in a microcontroller-based assembly language such as had to be used on the 8088-based IBM PC. That was proof to me that the Adventure game had been ported from a mainframe implementation.

  24. alex870

    Parsec and speech were fun

    I never really got into the Basic Interpreter for the TI-99/4A except for trying to invoke the speech synth. My friend had the TI, I had the BBC Model B. Once you used BBC Basic in anger, the rest of the Basic offerings from competing home computers of the era measured up pretty short by comparison. Using *LOAD to load a binary game, getting the memory addresses for *Save to write the binary out to cassette as a first generation copy. Good times for a 10 year old in the 80's!

  25. Steve B

    Great architecture but lousy design.

    We had a development system for the 9900 and just using 2K of program and 16K of RAM, I built a comms controller linking 8 screen based terminals and 4 printers to the ICL mainframes allowing us to use cheap dumb terminals saving tens of thousands per set up. We took the 99/4 onboard as a cheap device for our remote offices, but when we closely examined the architecture, we found that the memory was accessed through the video controller and not directly which made it a no no for serious development, ie replacing the operating system with my own! Instead we built our own rs232 interfaces and wrote basic programs which allowed the remote offices to input and edit their payroll data, sending it automatically to the mainframe and receiving and printing the processed response. The limitation was the use of cassette tape. I Still remember my first demo, suitably impressing the ladies in the remote office. Taking everything back to scratch and saying "right, your turn" showed the uphill task when the boss lady tried to force the cassette into the player whilst still in its case as they had not come across these new fangled cassette tapes before!

  26. Torben Mogensen

    Double interpretation overhead

    The main reason that BASIC on the TI99/4a was slow was that the BASIC interpreter was not written in assembly language (which would not have been difficult, as the TMS9900 was much easier to program than 8-bit alternatives such as 6502 or Z80), but in a language called GPL (Graphics Programming Language), which was compiled to a byte code that was interpreted by the CPU. I estimate the overhead of using interpreted byte code to be 5-10 times, so a BASIC interpreter written directly in assembly language would have sped up the BASIC enormously -- depending on what you do, though. For some operations such as floating-point calculation or graphics primitives, the overhead is relatively small, but for integer calculations it is pretty hefty. Games that are written in assembly language are not affected by this, but I still find it a curious design decision -- it made the TI99/4a compare very badly to other home computers in BASIC benchmarks, which is what most magazines used to compare speed of home computers.

    1. ForthIsNotDead

      Re: Double interpretation overhead

      There is a reason for the double interpretation. The TI-99/4 (and the later 4A, which has a better keyboard and a better graphics processor) was never intended to have a TMS9900 as its CPU. The intended CPU was going to be a custom made CPU that executed GPL as its native instruction set. The chip (it might have been the 9985, but my memory might be faulty) never made it, and after flirting with 8-bit CPUs such as the Z80, the 9900 was engineered in, on the grounds that TI would be damned if they would help Zilog by putting a Z80 in there, or Motorola etc.)

      However, by the time this decision was made, the mother-board had been designed, and it was all 8 bit. Extra hardware had to be added (the 8/16 multiplexor) to do two fetches from memory and present it to the 9900 as a single 16-bit word.

      It gets worse. Much worse. But no one would believe me, so I'll just leave it there!

  27. chivo243 Silver badge


    I have come into possession of a Commodore Pet 2001. I have not tried to boot yet, I'm told it doesn't. One thing I did check is the little glass fuse in the back, all looks good there. Now to find time to dig in...

    1. Anonymous Coward
      Anonymous Coward

      Re: Recently

      If you struggle to get it up and running, then speak to the guy at Tyynemouth Software ( He has repaired numerous PETs and also offers some great add ons such as a hard disk emulator that uses SD cards. You can program applications in C using the cc65 compiler on your modern machine, test them on the VICE emulator, then copy the binaries to an SD card and run it on the PET :-)

  28. Liam Proven Silver badge

    What no Geneve?

    Slightly surprised there was no mention of the Geneve 9640, a 3rd-party replacement motherboard that could be installed in the Peripheral Expansion Box to make it into a stand-alone computer. It delivered most of the improvements of the stillborn TI 99/8 and more, realising the potential of the TI.

    It was a very impressive upgrade and shows what TI could have done with the machine if it had stuck with it.

    1. Alan W. Rateliff, II

      Re: What no Geneve?

      Likely because the Geneve out-right replaces the 99/4A as a much more capable machine. It is compatible to a large degree being able to run pretty much everything from the old console, including "ripping" cartridges, and use the same hardware expansions. The Geneve is like the SuperCPU of the TI world, but a little easier to find, and I just picked up one at last year's Chicago TI Users Group Faire but like with all things time is my worst enemy.

      While a massive upgrade for the 99/4A, almost all of the major development in the forum is directed solely at the 4A console, even down to the bare-bones 256 bytes of CPU RAM and 9918A, only -- no 32k, etc. This is changing, though, to require 32k now that the nanoPEB and 32k sidecar expansions are pretty prevalent. Games and demos by Rasmus and a few others all require 32k, as do numerous Extended BASIC (following tradition of the Old Days when XB and 32k went pretty much hand-in-hand.)

      Maybe a future article could delve into the Geneve world and the salivating anticipation for the FPGA-based Geneve II. There are several experts on and developers for the Geneve around to help with that.

  29. ATE

    TI 9900 SBP

    Those of us who worked at TI North in those years used TI 9900 computers in an automated test environment. Some of the Airborne Radar Systems used TI 9900 processors. Look up the MRCA Tornado. TI was first to 16 bit architecture, but TI was a closed development culture and did not understand the advantage of open architecture.

  30. Simon Rockman

    Never did it for me

    I go misty eyed at most bit of kit but even in the day I never got the TI99/4a. How could somethin which was 16bit be so much slower than the 8bit computers?

    Then of course we got the QL (albeit with an 8bit bus) and found out.

  31. Anonymous Coward
    Anonymous Coward

    Was it really so short lived?

    I was convinced this machine remained a fixture throughout the 1980s - it seemed to be in every Argos catalogue for year after year after year...

    1. ForthIsNotDead

      Re: Was it really so short lived?

      1981 to 1983 then it was all over.

    2. Mark Dempster

      Re: Was it really so short lived?

      It was only MADE for 3 years, but sold so badly they were in UK shops for a lot longer...

      1. John Brown (no body) Silver badge

        Re: Was it really so short lived?

        "It was only MADE for 3 years, but sold so badly they were in UK shops for a lot longer..."

        I seem to have vague memories of it being massively expensive in the UK due to initial supplies being sold with a 60Hz monitor or an NTSC TV set since they'd not localised it for the UK. Am I mis-remembering?

  32. Pascal

    The first computer I owned...

    I had the occasional brush with an Apple IIe before (where I learned some very, well, basic BASIC), when Sears liquidated their stocks in ~83 or 84, my parents bought it for me.

    Soon enough, I had scrounged the extra peripherals - the speech synthesizer, the external expansion (with slotted RAM on an external bus AND a floppy) and, the grand prize of them all, an ASSEMBLER cartridge that basically gave you access to assembly coding.

    So there I was at ~12 years old, having only a few months of self-training in BASIC, learning assembly on the TI-99/4A with zero resources other than a 4-inches thick manual in english (which I needed a french-english paper dictionnary at the time to understand).

    Good times!

    That's what got me started anyway, so I still have great memories of this little computer.

  33. Herby

    Tried to compete with...

    The Radio Shack Color Computer ("CoCo") and really didn't do a reasonable job.

    The CoCo had a reasonable version of Basic when powered on, and could be purchased with a reasonable amount of memory (16k was available) off the shelf. It had a bunch of cartridges thad actually DID things you wanted to do (you could even get a spreadsheet one), and the whole thing was priced pretty reasonably. The CoCo even went through a couple of upgrades along the way. If you were really adventurous you could get OS-9 (cut down Unix "-ish") to work with floppy disks.

    Me? I bought a 4k model that lasted at 4k for about 1 hour after I opened up the box. I upgraded it to 32k before the day was done. Somewhere I still have the box buried somewhere, and it is at 64k bytes. The 6809 processor was a pretty good 8 bit CPU (probably the best overall!).

    Fun times.

  34. ScottV

    Loved this machine

    I wrote a couple of books for this machine back in the days, "Making The Most of your TI-99/4A" and "Dynamic Games for your TI-99/4A". I've still got a box full of 'em in my loft courtesy of the publishers. Not much demand for them these days!

  35. John Smith 19 Gold badge

    But what's not been mentioned is its relation to the transputer

    Stack based architecture with in memory register set.

    The biggest issue with the transputer seems to have been that word length equal to the address length. I was never really clear if this was a policy or just a rather bad design decision, given the common SoA was 8 bit processors with 16 bit addresses.

  36. Ian 55

    I remember it

    I remember it being crap.

  37. Paceman

    I have very fond memories of the 99/4A.

    When I was about 10 we emigrated to Lubbock, Texas as my dad took on the lofty-sounding role of Vice-President of Personal Computing (in fact there were several VP's, but it sounded good to me). This was back in 1982.

    We had a 99/4a at home (as you'd expect) and used to get early prototype's of things like the speech synthesiser, and games. The games weren't in cartridge form, they were a big box with a ribbon cable coming out of it, with a cartridge end that you plugged in the slot!

    Parsec was a great game, and the pac-man clone that had a kind of cheat option that let you pick any level - I seem to remember that on level 99 the walls were invisible (and because you left a path as opposed to eating one like Pac-Man) you needed a good memory of the map!

    Happy times!

    Sadly, as has been pointed out, the short-lived lifespan of the 99/4a and in fact the Home computer Division as a whole meant we weren't in Texas for long. My dad got another job in California working on the original Apple Mac. Unfortunately that didn't last as my old man was not a big fan of Jobs!

    Wish I'd been able to hang on to some of the kit that used to come through the house, I might be worth something!

    1. Milo Tsukroff

      The PacMan clone..

      > the pac-man clone

      was Munchman. Our first video game! My kids and I played that for HOURS. That, and Parsec, were the world to us. Unfortunately the crappy construction on the joysticks caused them to fail. We went through at least 3 sets, until we got the adaptor that allowed using an Atari-style joystick. Joysticks with microswitches worked much better. We broke a few of those, also.

  38. Dabooka

    Similar things are done on CPCs

    Over at CPCWiki there's the same kind of stuff going on; 'jukebox' carts for the short lived GX4000 gaming system (and the CPC+ models), the ubiquitous HXc floppy emulators and others including IDE HDDs, alternative ROMs, 4MB expansions, etc. And of course loads of new software

    I was amazed when I had a Poke about....

  39. MT Field

    The TI9900

    If I remember correctly this was a novel processor design that was RISC-like in implementation and well ahead of the curve in that respect. Also it used blocks of main memory as the register set which allowed for rapid context switching. So there were clever guys working in an American company and the rest is history.

    1. Roo

      Re: The TI9900

      "Also it used blocks of main memory as the register set which allowed for rapid context switching."

      The INMOS T2/4/8s took a similar approach - and they were also *very* quick at context switching.

    2. ForthIsNotDead

      Re: The TI9900

      Yes. You use the LWPI (Load Workspace Pointer Immediate) instruction.

      Eg LWPI $A000

      Now, your 16 16-bit registers (R0 to R15) start at $A000 in RAM.

      If you later did a BLWP (branch and load workspace pointer) instruction, R13, R14, and R15 in the *new* register set contain the status register, program counter, and workspace address of the *previous* workspace/context, so you can return to where you were, with the old context fully restored.

      It's a lovely system.

  40. StudeJeff

    Parts at Radio Shack

    When TI discontinued the TI-99/4A they must have had a LOT of parts left over. It seemed like for years Radio Shack had TI-99/4A bits for sale. I must have bought a half dozen or so of the power supply boards, I think they were something like $5, and they were nice power supplies.

  41. GruntyMcPugh

    Mate of mine had a TI99/4a, remember there was a decent port of 'Defender' that kept us quite amused. I kind of miss those days, I had an Acorn Electron, other school chums had different machines, BBC model 'B', Commodore 64, Dragon 32, Amstrad CPC, Spectrums in various guises, we went around each other's houses to discover what each machine could do. And before you ask, yes, we played D&D, and no, I wasn't the chubby one.

  42. Grunchy Silver badge

    Bah TI wasn't any good

    There was one TI-99 in high school, but it wasn't worth the time. Too underpowered, too lame. The physics dept had it, but I never saw anybody doing anything in earnest on it.

    The business education dept. had an entire lab of Commodore Pets !

    (We made the very first malware there - by rapidly POKEing the video adapter into different modes, we got the video chip to overheat - we ran this on every PET in the lab over lunch break, afterwards the lab teacher came back to a room full of smoke and pricey machines seemingly destroyed - off/on and back to work with yew! No lasting damage, that's how good Commodore equipt. was back in the day.)

    The *real* retro machine was the Vectrex. I actually got one, years & years after they had been discontinued, and bought the combo cart (with every single game ever released on one menu-accessible cart).

    A few years later I was like "man what's up with this old junk" and pitched it.

    Moving on ....

  43. cashback

    Happy memories

    I too had one. I remember the graphics being quite advanced at the time, the BASIC had sprite capability I believe.

    Me and a mate wrote a Connect 4 game for it and had it published in a Computer mag, I remember getting a letter back from Robert Schifreen who was working there at the time. He went on to "other projects" :D and gained some notoriety!

  44. zappy

    First computer, right here

    Wow, yep, this was the first machine I ever had. My old man worked retail and brought a (discontinued) one home for three-year-old me. He soon connected me with a workmate of his who'd gone fully-loaded-peripheral-box-crazy over these things, and who promptly drowned me in software and know-how. The Speech Synthesizer was especially fun - I remember being able to feed it phonetically-spelled text that sounded pretty natural - especially for the mid-80's.

    I still love the robotic-chicken noise of the tape recorder reading in a tape of, say, Tunnels of Doom. Sounds like home.

  45. Anonymous Coward
    Anonymous Coward

    99/4A Sprites!

    I had a 99/4A as my 2nd or 3rd computer (I don't remember if I had it right before or after the OSI C1P but it was after the Netronics 1802 Elf). I totally loved the advanced graphics ability it had, using sprites as independent objects. But the cost of the expansion chassis and modules prevented me from hanging on to it for very long. For years afterward I used other peoples mainframes via Hazeltine 1420 or LSI Adm3A terminals until I managed to get a Mac IIx with A/UX

  46. Glenn Amspaugh

    Still Got Mine!

    I have a beige Ti99/4a and it still runs great. Just wish I hadn't left my data cassette in the cassette player, and then stored in the attic for 20 years. It snapped, trying to read.

    I'd coded a flat file Traveller ship database on there, with vector drawn deck plans, as well as a D&D character generator and of course, a dice roller. I also had a 4 channel conversion of Steven Howe's Mood For A Day. No, not a nerd, not nerdy at ALL!

  47. Anonymous Coward
    Anonymous Coward

    The machines look cool. All the games are pretty shite and nothing an emulator won't help with.

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