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UNIX99, a UNIX-like OS for the TI-99/4A (2025)

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Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#41

Post by HappMacDonald »

PaulHoule wrote: post #29
SoftTalker wrote: post #13

Earlier quoted context omitted.

It's cool because the registers are all in RAM, with a "workspace pointer" on the CPU pointing at where they are. This is slow, but a context switch is just changing that pointer.

Well, it has 256 bytes of RAM which is basically a really big register file, and everything else goes in the 16kb of "video RAM" which you can read and write by poking at I/O registers. So it is not easy to program. It's arguably the only 8-bit computer which has a really different architecture from the others. You could otherwise imagine pulling the SID chip off a C-64 and putting it on a TRS-80 Color Computer etc.…

Well I mean it fits in with the 8-bit era machines as far as performance but that CPU was absolutely 16 bit.

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#42

Post by guptadeepak »

Interesting project. IIRC, one of the biggest challenges with the TI-99/4A was its TMS9900 processor. It was a 16-bit CPU, but had a really awkward memory architecture that made it difficult to write efficient code.

The lack of dedicated registers meant a lot of memory access, which slowed things down considerably. This is probably why it never gained the same traction as the 6502-based systems like the Apple II or Atari.

I'm curious to see how this UNIX-like OS addresses those limitations. It's a pretty neat accomplishment if it can provide a usable environment on that hardware.

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#43

Post by PaulHoule »

HappMacDonald wrote: post #41
PaulHoule wrote: post #29

Earlier quoted context omitted.

Well, it has 256 bytes of RAM which is basically a really big register file, and everything else goes in the 16kb of "video RAM" which you can read and write by poking at I/O registers. So it is not easy to program. It's arguably the only 8-bit computer which has a really different architecture from the others. You could otherwise imagine pulling the SID chip off a C-64 and putting it on a TRS-80 Color Computer etc.…

Well I mean it fits in with the 8-bit era machines as far as performance but that CPU was absolutely 16 bit.

16-bit registers, operations, etc. yeah. A bigger machine of the TM9 series would be more like a PDP-11.

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#45

Post by alienbaby »

ectospheno wrote: post #14
SoftTalker wrote: post #9

@UsagiElectric on YouTube has a series of videos on building a homebrew around the TMS9900 processor. Would be cool if a unix-like OS could be used on something like that, though sounds like this project is specifically targeting the TI-99/4A system. The TI-99/4A was the first computer I owned as a teenager. I had used TRS-80s and Apple ][ at school. I eventually bought the expansion box and a couple of accessory car…

I had one in grade school. Taught me the value of backups early in life. Spent all night typing in a game from a magazine. Started it without saving to tape first. It was so loud! Panicked and restarted the machine. Sadness ensued. Replaced it with a C128-D. Didn’t get my first intel until I bought a 386 after graduating high school. Good times.

I feel this

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#46

Post by shiroiuma »

arnonejoe wrote: post #33

For some reason I was thinking it was that $99 dollar Sinclare from the 80s which had the most unusable keyboard on earth.

The TI's keyboard wasn't great either, but it was a lot better than the keyboard on its predecessor, the TI-99/4 (no 'A').

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#47

Post by badc0ffee »

PaulHoule wrote: post #43
HappMacDonald wrote: post #41

Earlier quoted context omitted.

Well I mean it fits in with the 8-bit era machines as far as performance but that CPU was absolutely 16 bit.

16-bit registers, operations, etc. yeah. A bigger machine of the TM9 series would be more like a PDP-11.

In fact it was a miniaturized TI-990 minicomputer: https://en.wikipedia.org/wiki/TI-990

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#48

Post by badc0ffee »

UncleOxidant wrote: post #17

So assuming one wanted to buy a used one of these (I had timex sinclairs around this time) how would one display the composite video nowdays?

You can still buy portable DVD players with a laptop-sized screen, with composite in.

Other than that, you can buy relatively inexpensive converter boxes that take composite video and analog audio, and output HDMI.

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#49

Post by lioeters »

tombert wrote: post #44

Interesting. This sort of reminds me of Lunix [1]. [1] https://lng.sourceforge.net/

> LNG is an operationg system primarly for the good old Commodore64 home-computer. There also is a native version for the successor Commodore128. Ports to other 6502/6510 driven 8Bit Computers are possible but not yet started. LUnix started in 1993 and reached the internet in 1994.

That is old-school cool.

Re: UNIX99, a UNIX-like OS for the TI-99/4A (2025)

#50

Post by tombert »

lioeters wrote: post #49
tombert wrote: post #44

Interesting. This sort of reminds me of Lunix [1]. [1] https://lng.sourceforge.net/

> LNG is an operationg system primarly for the good old Commodore64 home-computer. There also is a native version for the successor Commodore128. Ports to other 6502/6510 driven 8Bit Computers are possible but not yet started. LUnix started in 1993 and reached the internet in 1994. That is old-school cool.

I'm not sure how practical it actually is, but I did play with it in an emulator and it's pretty impressive for what it is. I mean, the C64 really should not be capable of preemptive multitasking, but they somehow pulled it off.

It's extremely slow, which isn't surprising, but I still think it's pretty neat.

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