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

The joy of computing still lives in the age of AI...

WoW!

made me remember knightOS

https://github.com/KnightOS/KnightOS

This is the main updated comment with the user guide and download

https://forums.atariage.com/topic/380883-unix99-a-unix-like-...

Wow. The TI-99 is such a perfect fit for this too given the chip was designed for multi-user computing in a way other home computer chips weren’t.

All due to TI’s desire to use the same chip standards across all their machines big and small, IIRC.

Imagine a Beowulf cluster of these.

@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 cards (floppy disk drive, memory and RS232). It all went in the e-waste dumpster about 20 years ago during a move.

Does it run PARSEC? Nice shot captain!

HOLY COW. Thank you for this. I LOVE the Ti99/4a, its one of the first computers I ever used. I've got one up and running at home now currently and can't wait to try this.

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?

I learned to program on this exact hardware in the early 80s as a small child. It uses BASIC. It's hard drive was modem tones recorded to an analog audio tape. Its monitor was an analog TV. There was no mouse. The keyboard was built into the computer itself.

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

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.

Interesting. This sort of reminds me of Lunix [1].

[1] https://lng.sourceforge.net/

What features does one specifically mean by "UNIX-like"? Unified filesystem with a single root? A CLI shell with the classic abbreviated comands? Preemptive multitasking? Multiuser-oriented permissions?

I'm still happy about FUZIX on the RP2040 (last discussed here two month ago https://news.ycombinator.com/item?id=46271115 ). A capable SoC that costs around $1. Only via (USB) serial so far, but that works for me.

I wish there were some cheap FPGA version of the 3rd party implementation of the planned successor, the TI-99/8.

It was called the Geneve 9640 from Myarc:

https://dressupgeekout.com/geneve/

http://www.mainbyte.com/ti99/geneve/geneve.html

Wikipedia has a decent article:

https://en.wikipedia.org/wiki/Geneve_9640

12 MHz un-crippled 16-bit CPU, 80 column text, 256 colour graphics, up to 2 MB of RAM.

That would be much more promising for a Unix-like OS!

They are extremely rare these days, but a cheapo emulation would be great fun -- it's able to run most software for the 99/4A.

I wonder if this kind of architecture would be fun to build an L4 microkernel based system with.

Context switching and message passing (synchronous anyway) are the same thing when you consider how rendezvous works.

BLWP instructions seem like this was “meant to be”.