4 ms·

TI-99/4A: Leaning more on the firmware

77 points by ibobev 10mo ago

hammad67 10mo ago
[dead]
zombot 10mo ago
I had to look up TI-99/4A. Are there still TV sets today you could connect this to?
- diputsmonro 10mo ago
  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 10mo ago
  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 10mo ago
  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 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 10mo ago
  Use a balun and just hook it up to where you usually connect the rabbit ears.
- NoMoreNicksLeft 10mo ago
  If you had the expansion bays, some guy released a limited run of vga (cga?) graphics boards for it a long time ago.
- timbit42 10mo ago
  You could get a RetroTink to convert it to HDMI.
- badc0ffee 10mo ago
  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 10mo ago
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_Instruments_TI-99/4A#/media/File:2015-09-22_Computerspielemuseum_Berlin_08.jpg https://commons.wikimedia.org/wiki/Category:Texas_Instrument...
- genewitch 10mo ago
  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 10mo ago
    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 10mo ago
userbinator 10mo ago
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 10mo ago
  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 10mo ago
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 10mo ago
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 10mo ago
  I had a C64 and learned programming on it. I guess it's a question of destiny at this point :)
- eesmith 10mo ago
  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 10mo ago
    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 10mo ago
    >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.
msarrel 10mo ago
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.
- incanus77 10mo ago
  Yes, same here. I have this setup replicated and do demos for people whenever there is interest. It's the strongest connection I have to the arcane old ways of computing as I came after punch cards and paper tape.
Dwedit 10mo ago
The MSX was basically the TI-99/4A done properly. Just use a Z80 instead of whatever mess they were using.
- tliltocatl 10mo ago
  But 9900 wasn't a mess. It was a very nice minicomputer-grade CPU. 99/4A problem wasn't the CPU, it was that it was designed as a game console and tried to pass up as a computer.
cbm-vic-20 10mo ago
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=PLnw98JPyObn0XjXzHHWr2p4_a2zBT3KYR&index=10 https://www.youtube.com/watch?v=ADigs7hlLTM&list=PLnw98JPyOb...
deleted 10mo ago
[deleted]
muziq 10mo ago
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..

77 points by ibobev 10mo ago

hammad67 10mo ago

[dead]

zombot 10mo ago

I had to look up TI-99/4A. Are there still TV sets today you could connect this to?

diputsmonro 10mo ago
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 10mo ago
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 10mo ago
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 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 10mo ago
Use a balun and just hook it up to where you usually connect the rabbit ears.
NoMoreNicksLeft 10mo ago
If you had the expansion bays, some guy released a limited run of vga (cga?) graphics boards for it a long time ago.
timbit42 10mo ago
You could get a RetroTink to convert it to HDMI.
badc0ffee 10mo ago
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 10mo ago

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_Instruments_TI-99/4A#/media/File:2015-09-22_Computerspielemuseum_Berlin_08.jpg https://commons.wikimedia.org/wiki/Category:Texas_Instrument...

genewitch 10mo ago
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 10mo ago
  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 10mo ago

userbinator 10mo ago

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 10mo ago
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 10mo ago

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 10mo ago

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 10mo ago
I had a C64 and learned programming on it. I guess it's a question of destiny at this point :)
eesmith 10mo ago
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 10mo ago
  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 10mo ago
  >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.

msarrel 10mo ago

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.

incanus77 10mo ago
Yes, same here. I have this setup replicated and do demos for people whenever there is interest. It's the strongest connection I have to the arcane old ways of computing as I came after punch cards and paper tape.

Dwedit 10mo ago

The MSX was basically the TI-99/4A done properly. Just use a Z80 instead of whatever mess they were using.

tliltocatl 10mo ago
But 9900 wasn't a mess. It was a very nice minicomputer-grade CPU. 99/4A problem wasn't the CPU, it was that it was designed as a game console and tried to pass up as a computer.

cbm-vic-20 10mo ago

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=PLnw98JPyObn0XjXzHHWr2p4_a2zBT3KYR&index=10 https://www.youtube.com/watch?v=ADigs7hlLTM&list=PLnw98JPyOb...

deleted 10mo ago

[deleted]

muziq 10mo ago

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..