[HN Gopher] TI-99/4A: Leaning More on the Firmware
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TI-99/4A: Leaning More on the Firmware
Author : ibobev
Score : 69 points
Date : 2026-01-18 23:19 UTC (4 days ago)
(HTM) web link (bumbershootsoft.wordpress.com)
(TXT) w3m dump (bumbershootsoft.wordpress.com)
| zombot wrote:
| I had to look up TI-99/4A. Are there still TV sets today you
| could connect this to?
| diputsmonro wrote:
| IIRC it just outputs video as a composite signal over RCA, so
| any TV with composite inputs (yellow/red/white) should be able
| to display it. Those are getting rarer I suppose but are
| generally still around, and most CRTs have them.
| fredoralive wrote:
| New TVs often don't have analogue inputs, so you'd need some
| sort of analogue to HDMI scaler, which range from aliexpress
| tat to expensive enthusiast stuff like Retrotinks, with various
| hobbyist stuff like OSSC in between as well. Some really old
| stuff is RF only, so you might need a tuner as well (or an old
| VCR) to go from RF to baseband composite.
|
| Older LCDs will probably have RCA inputs though they might not
| work with all retro computing stuff as the signals are
| sometimes rather "non standard" (not sure about this particular
| case).
|
| CRT TV should be fine, as they're from the right era and a bit
| less fussy about signals.
| myself248 wrote:
| The computer includes an RF modulator, so you need a TV that
| can tune NTSC channel 3 or 4.
|
| Or, buy a DIN plug and make a cable that brings out the
| composite signal: https://99er.net/TIvideoadapter.htm
|
| I haven't bought a _new_ TV recently, but there seems to be no
| shortage of composite inputs on the sets I 've been using.
| bregma wrote:
| Use a balun and just hook it up to where you usually connect
| the rabbit ears.
| NoMoreNicksLeft wrote:
| If you had the expansion bays, some guy released a limited run
| of vga (cga?) graphics boards for it a long time ago.
| timbit42 wrote:
| You could get a RetroTink to convert it to HDMI.
| badc0ffee wrote:
| I recently had to help a friend (not in the same city) look for
| a way to use the composite video output from an Apple //c. New
| TVs and monitors don't support that input anymore, and the
| thrift stores were empty of old ones. What ended up working was
| a portable DVD player (!) as you can still buy these new, and
| they still have composite in for some reason.
| TacticalCoder wrote:
| TFA lacks a picture of the TI-99/4a. I've got one and it's such a
| beautiful machine:
|
| https://commons.wikimedia.org/wiki/Category:Texas_Instrument...
| genewitch wrote:
| I convinced my grandfather to give me $30 to buy one at a
| garage sale while i was house sitting with him (he had
| emphysema and was 82 at the time) back in the early 90s. he
| lived as an adult through the depression, so it was a point of
| contention between him, me, and my mom. It only came with 1
| cartridge iirc, and a brochure showing all the accoutrements
| you could add to it, speech module, joystick, and i forget what
| else.
|
| turning it on and getting a BASIC prompt was real cool. never
| could save anything, though. I traded it in 1999 or so for an
| Apple IIc with monitor, with which i could save data.
|
| coincidentally, i just mentioned owning a ti-99/4a to a friend
| yesterday, we were comparing notes about the first computers we
| actually owned, and that was it, for me. We had an atari (the
| wood paneled console one, carts, with keyboard built in, BASIC
| interpreter on ROM) in '87ish i guess, but i only had it for a
| couple of weeks before i accidentally blew it up with a cable
| trying to save something to a tape recorder. the tape recorder
| had a cable in the back that had a 1/8" TS plug, which
| apparently was a radio shack "universal power supply" and i
| guess i put 9VDC into the speaker port.
| eesmith wrote:
| To save you either needed a cassette recorder, plugged into
| the machine with a special cable, then "SAVE CS1" and follow
| the instructions. (Start recording, the TI plays sound to the
| output port, which gets stored on tape. Use "LOAD CS1" to
| load from cassette, after rewinding to the start of the
| program.)
|
| Or you needed an expansion box, with a floppy drive, in which
| case you could do "SAVE DSK1,PROGNAME" to save to "PROGNAME"
| on the first disk. I didn't have an expansion box.
|
| Neither would have come with the base computer.
| endgame wrote:
| The command to load a program in TI BASIC was actually "OLD
| <DEVICE>". Probably because they already had "NEW".
|
| https://www.ninerpedia.org/wiki/TI-99/4A_system_usage#Loadi
| n...
| eesmith wrote:
| My 40 year old memories are indeed faulty. Thanks for the
| correction!
|
| FWIW, I probably confused it with Commodore Basic, since
| part of me wanted to put a ",1" at the end of the load
| command.
| timbit42 wrote:
| The reason it had the OLD command is because the original
| version of BASIC, Dartmouth BASIC, had the OLD command.
|
| Microsoft BASICS didn't have it.
| 83457 wrote:
| I believe it was also the Mini Memory cart where you could
| save programs, backed by a replaceable battery inside.
| mrandish wrote:
| There was also a beige version released later
| (http://www.mainbyte.com/ti99/computers/ti99beige.html). I have
| both variants in my collection and they're both attractive
| machines, especially by the standards of the early 80s. The
| best part of the design was that it had a decent keyboard
| (unlike its predecessor the TI-99/4, which is much more rare -
| and for good reason). It also was the first home computer to
| have hardware graphics support in the form of TI's home-grown
| TMS9918 VDP chip which outlived the computer it was made for by
| many years. It was used in dozens of different 8-bit computer
| models from manufacturers around the world and spawned several
| improved variants, including the graphics chip in the Sega
| Master System console!
|
| Unfortunately, the 99/4a was brutally hobbled by some bizarre
| design choices that nerfed its performance including forcing
| the 16-bit CPU onto an 8-bit system bus which halted the CPU to
| spread each 16-bit read/write into two sequential operations.
| This was made worse by the fact the CPU used a memory-to-memory
| architecture (even for most of its own registers) and all the
| memory was behind that '8-bit wall' - except for 256 bytes of
| 'fast scratchpad' (aka just 'normal memory' on other 8-bits).
| Plus the GROM was on PROM chips that were even slower than RAM,
| introducing more latency.
|
| The whole GROM thing _could_ have been a nice idea if it weren
| 't for the 8-bit bus and slow PROM chip speed. Unfortunately,
| TI execs were more interested in finding a home for excess PROM
| chip inventory than making their home computer the best it
| could be. So, it was hard to extract high-performance game
| graphics from the system, requiring significant ingenuity from
| developers.
| genericacct wrote:
| It was The original brushed metal computer.
| userbinator wrote:
| _an ordinary part that mapped into 8KB at location >6000->7FFF
| (the ROM) and another part, that normally held Graphics
| Programming Language bytecode, mapped into a completely separate
| "Graphics ROM" address space from >6000->F7FF (the "GROM")._
|
| This reminds me of the NES, which has separate PRG and CHR
| address spaces, the latter being exclusively for the PPU to
| display its graphics.
| bregma wrote:
| It's not quite the same.
|
| The TI-99/4 has 4k of scratchpad RAM accessible to the CPU. The
| CPU architecture had no general-purpose registers and had
| basically only 3 onboad registsrs: the status register, the
| program counter, and the workspace pointer. The WP pointer to a
| 32-byte range of RAM that worked like a set of 16 16-bit
| registers and a subroutine call was a matter of storing the
| current PC and WP and loading a new pair (a whole new set of
| registers). The 4k RAM was the equivalent of "the stack" on a
| modern x86 or Arm CPU.
|
| Programs were stored as bytecode in memory addressable only by
| the graphics processors (note: not a GPU). Executing a program
| meant the CPU would write the GROM address to a register on the
| graphics chips followed by a request to fetch and would then
| read the byte from another register. It then had to interpret
| that byte through the ROM.
|
| There were true separate address spaces, not different ranges
| in the same flat address space like on the NES. The CPU could
| not address the GROM directly.
|
| I had the Minimem cart that had a line-by-line assembler that
| let me dump the ROMS. Many hours were spent hand-disassembling
| the OS for my TI-99/4A.
| shawn10067 wrote:
| I love reading about classic machines like the TI 99/4A. Leaning
| on firmware to squeeze out more capability is such a clever way
| to extend hardware from that era.
| matthewsinclair wrote:
| Ah, the TI-99/4A. My first computer. What a mercurial beast of
| thing that was. I desperately wanted a C64 for Xmas but my Dad
| was somehow convinced to buy one of these. It had about 4 games
| (including "Hunt the Wumpus") and so instead of playing the
| myriad C64 games that all my mates were playing, I was forced to
| learn BASIC and try to write my own! 45 years later, I'm still
| programming.
| onurcel wrote:
| I had a C64 and learned programming on it. I guess it's a
| question of destiny at this point :)
| eesmith wrote:
| My Dad was convinced by the marketing that its 16-bit CPU was
| the wave of the future, unlike those old-fashioned 8-bit CPUs.
|
| It had a smidge more than 4 games. I broke several joysticks
| playing TI Invaders, and my favorite was Parsec, which was also
| one of the games which supported the optional speech
| synthesizer. I also had Tunnels of Doom, Car Wars, and
| Tombstone City, and remember playing Alpiner.
|
| That's 6 games right there, ... or in other words, a drop in
| the bucket compared to my friend's Apple ][. Alas. And he could
| use a floppy disk, while I only had cassette tape or
| cartridges.
|
| One of my game cartridges was Extended Basic. That probably got
| the most use.
| roelschroeven wrote:
| I distinctly remember my dad too choosing for the TI-99/4A
| over the competition because of the 16-bit CPU. Little did
| he, let alone the little boy that I was at the time, know of
| the limitations of its weird design.
| NoMoreNicksLeft wrote:
| >My Dad was convinced by the marketing that its 16-bit CPU
| was the wave of the future,
|
| I think my mom was convinced because of bargain bin prices
| after it was more or less dead as a platform. But I'm not
| sure, she's not around to ask anymore... I've read though
| that after TI gave up on it, some department stores were
| dumping them for well under $100, and sometimes closer to
| $50.
|
| I think I only once, ever, got it to load a saved program
| from cassette. I don't know if I was just a moron as a kid,
| or if they were actually that horrible for storage.
| pm215 wrote:
| Tape save and load seemed pretty reasonable on our system.
| It does depend rather on the tape deck you're using and
| also on getting the volume and tone settings right, though.
| We had the official TI tape deck for it.
| qmr wrote:
| I am so, so sorry.
| PeterStuer wrote:
| The TI-99/4A was the first computer around here that was
| affordable (wanted the Apple II but that was priced way out of
| my league). I never got any cartridges, used the family TV as a
| monitor (so no evening computing) and for the first month or so
| had no tape deck (so programming on paper and retying at every
| session).
|
| The included manual for programming BASIC was extremely well
| written, and it's sprites made it very easy to write your own
| games. I remember starting with a multi-player 'snakes'
| variant, a 'defender' clone, an unfinished chess game (ran out
| of memory), and top down microcar racing game.
|
| I also remember longing for the UCSD/Pascal cartridge as all
| (library) books I read used Pascal in their coding examples,
| but it was too expensive.
|
| I later switched to the ZX Spectrum for which I had HiSoft
| Pascal, and a burnt in bare black&white monitor sold for scrap
| from an old arcade game.
| eesmith wrote:
| > used the family TV as a monitor (so no evening computing)
|
| I was allowed to program during ad breaks, typing in code I
| wrote out while the family was watching a show. :)
|
| I too remember the manual as being very well written. As I
| recall, it had tables on the back with frequencies for
| different notes, and foreground/background colors which went
| well (and not well) together.
| butterisgood wrote:
| I still see "INCORRECT STATEMENT" in my dreams.
| Damogran6 wrote:
| Wow...I learned UCSD/Pascal on the Amiga in High School, that
| takes me back.
|
| Edit: Hmmmm, might have been the Apple II. Not seeing the
| Amiga in the Wiki...We started on Apples, then migrated to
| Amigas Junior Year
| emadb wrote:
| I had the same exact story. My dad chose the TI instead of the
| C64 and the lack of games forced me to learn programming.
| holri wrote:
| same story here :-)
| kwanbix wrote:
| This was my first computer too! I loved it - that's where I
| learned LOGO. In my home country, games (and basically
| everything) were incredibly expensive, but my father still
| bought it from a friend who was selling it to upgrade to a C64.
|
| I remember playing Parsec, and Space Invaders. I am sure I had
| 2 or 4 more games. But don't remember which ones.
| vikingerik wrote:
| Parsec still rocks hard. I got good enough to roll over the
| score on it: http://dos486.com/misc/parsec.jpg
| matthewsinclair wrote:
| Parsec! And what about "Tunnels of Doom [0]" !? I spent so
| much time on that thing.
|
| [0]: https://en.wikipedia.org/wiki/Tunnels_of_Doom
| butterisgood wrote:
| Uh... brother?!
|
| Just kidding... That sounds like my journey as well. I had
| friends in the neighborhood who also had the TI-99/4a. We all
| had Cub Scouts and Boy's Life magazine listings to key in.
|
| Did you have the data cassette recorder? We used to try to
| "load programs" from Michael Jackson's Thriller album.
| matthewsinclair wrote:
| Yep. Totally. And there was this dreadful wait for a load
| that could (randomly) fail and you'd need to go thru the
| whole process again!
| incanus77 wrote:
| Same!
|
| My earliest memory of anything computer programming is from the
| early 80s, when a snow day had the two neighbor kids, whose
| parents were teachers in another district, over to our house
| with their TI-99/4a. The oldest showed me the entry and running
| of the sample program Mr. Bojangles. I was enthralled.
|
| A few years later I had one of my own, though at that point it
| was very long in the tooth. But I still learned its limits,
| playing (yes) Hunt the Wumpus, Tombstone City, and others,
| programming, and doing things like composing the Jeopardy!
| theme song in BASIC.
|
| I have one of these again, with the stuff I had as a kid, and
| more (like the voice synth) and it's so limited even for the
| era, but still iconic.
| mrandish wrote:
| > I have one of these again, with the stuff I had as a kid,
| and more (like the voice synth) and it's so limited even for
| the era, but still iconic.
|
| Growing up I had a retired uncle who'd collected and restored
| a few classic cars of the 1950s to cherry condition. He kept
| them in a separate four car garage out back where he'd work
| on them in his spare time and then take them out for a drive
| on Sundays. Being a nerd kid, I couldn't really relate. Those
| old cars couldn't go very fast, weren't very comfortable and
| didn't have important features like an 8-track tape player
| (oh, and seat belts). Even the radio was only AM! I was more
| interested in the latest Amiga computer, so my Uncle's deep
| affection for these old old cars was just a quirky
| eccentricity.
|
| Starting in the late 90s I gradually began acquiring classic
| 8 and 16-bit home computers of the 1980s when I'd hear of
| someone throwing one away. To me, that now-useless trash was
| still a treasure! At first I just "saved" the ones I'd
| actually owned but once I had those, I expanding to the
| models my teenage self had lusted over in Byte Magazine but
| could never dream of affording. eBay and thrift stores circa
| 2000 were overflowing with them for $5 or $10.
|
| Once I had all those, I just kept going and picked up every
| model I'd ever even _heard_ of and then a bunch of foreign
| ones from Europe, Japan, South America, Eastern Europe and
| Russia I 'd never heard of. And I never paid more than $25
| for any of them. They were just so interesting, I couldn't
| resist. Each platform was a unique evolutionary branch with
| its own opinionated design choices, operating system and
| vision of what 'personal' computing might be.
|
| So... _now_ I can finally understand my Uncle 's fascination
| with his weird, old, not-very-good cars. :-)
| pm215 wrote:
| I'm pretty sure my Dad got ours because they were being sold
| off very cheaply after TI pulled out of the home computer
| market. Like you I ended up learning BASIC on it because as an
| abandoned system all we had was a few cartridge games, some
| user-group programs, and typed in BASIC. It worked out pretty
| well really. (Later we got an Amstrad CPC 6128, which had a
| much bigger commercial games market.)
| msarrel wrote:
| The strangest thing I remember about my ti-99 was that I used to
| run software off of cassette tape. It was a good way to get
| games.
| Dwedit wrote:
| The MSX was basically the TI-99/4A done properly. Just use a Z80
| instead of whatever mess they were using.
| cbm-vic-20 wrote:
| If you're into this, you may be into a series on the Usagi
| Electric YouTube channel where he's building a homebrew computer
| based on the TMS9900 processor from the TI-99/4A.
|
| https://www.youtube.com/watch?v=ADigs7hlLTM&list=PLnw98JPyOb...
| muziq wrote:
| Commodore fanboy at heart, but maximum love to the weird uncle of
| home computing.. I was so jealous of Parsec on that, speech and
| all, in 1982, when our local nerd group used to go and stare at
| computers after school..
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