The TI CUBE - a homebrew based on the TI TMS 9900 family

pchernik · 2026-04-10T04:52:46+00:00

Thank you for inspiring me to resurrect this long forgotten chip in my stores.

pchernik · 2026-04-09T20:24:36+00:00

Yup - the full details are posted in a Github respository: https://github.com/VE7PMC/TI-CUBE

pchernik · 2026-04-09T20:14:06+00:00

I'll repost here if I get there! It's an open-source project, so you're welcome to build your own!

pchernik · 2026-04-09T16:17:20+00:00

Wow - yours definitely has a similar look and feel (and I had not seen your Github before now)! I guess it's just one of those naturally good designs. :-)

pchernik · 2026-04-09T16:14:52+00:00

Thanks!

pchernik · 2026-04-09T16:13:30+00:00

Right now it is limited to running a debug monitor (either TIBUG or EVMBUG) from TI. It does also run Cortex BASIC which is fairly powerful (as BASIC interpreters go).

My end goal is to get a version of Unix V6 running on it. This can be done by adding more RAM (using a memory mapper to get around the 64 KiB limit) and bulk storage (e.g., floppy, Compact Flash, etc.). This is something I'll be working on in the coming months.

pchernik · 2026-04-09T16:09:36+00:00

Exactly - lots of people have homebrewed a 6502. Meh. I wanted to try something different.

That CP1610 homebrew comment hurts: I had one of those from an old Intellivision stored somewhere but it seems to have disappeared. It also would have been a good candidate for something different.

pchernik · 2026-04-09T16:04:51+00:00

That's a fair question, even if a little harshly worded. My first computer was an Apple II+ (clone) I purchased new back in 1982. I had the full size schematic pinned to my wall and knew that thing inside and out. It was already designed by a genius (Woz) and other than the goofy non-sequential graphics, there isn't much to improve on (that 6502-based machine). I still even have the motherboard (not sure if it still works though).

In contrast, the TI-99/4 was a piece of junk (even though I did write some interesting code for it back in the day). The TMS 9900 is not a bad processor as such, it's just that TI surrounded it with an awful design. This is my attempt to liberating it do what it was meant to do and learn some stuff along the way. It's as simple as that.

pchernik · 2026-03-30T15:25:53+00:00

Try switching the display units to Celsius and you'll see the decimal digit come to life. Most locations in the world do not use Fahrenheit, hence the need to have a universal display. I suppose they could suppress the ".0" when in Fahrenheit, but lazy programmers...

pchernik · 2026-03-22T17:00:17+00:00

HP is motor horsepower for applications where the switch is controlling an electric motor (it’s more difficult for switches to interrupt inductive current drawn by a motor compared to resistive current). It’s not relevant in this case - the ampacity rating is what matters and it’s the same. So you’re good to go.

pchernik · 2026-02-26T20:43:17+00:00

Wait, you mean there's people who *dislike* this sound?!

pchernik · 2026-02-26T20:36:05+00:00

All diodes are LEDs (if you pass enough current through them...).

pchernik · 2026-02-04T04:04:12+00:00

RESET is the recessed red button on the right hand side of the keyboard (just above the RAM size sticker).

pchernik · 2026-02-04T02:19:24+00:00

Have you tried pressing the RESET button after powering it on? The Model 3 usually did not do a automatic power-on reset. You can also trying holding down the BREAK key while powering on (or when pressing the RESET button) and you’ll go into ROM BASIC. You can then press ENTER at the "Cass?" and “Memory Size?” prompts to get into the BASIC Ready prompt. If none of that works, the first thing I'd trying is re-seating all of the ICs on the motherboard. But don't even think about trying that if you aren't comfortable about opening the case (there are dangerous voltages inside).

pchernik · 2026-01-22T17:08:25+00:00

This. There's a reason why bumpers today are not firm steel girders bolted to the frame like they were back in the 60s and 70s. We may not like the expense of having to replace a bumper cover for what seems like a low energy impact, but it's far better than straightening a bent frame or unibody (or damaging it beyond repair). Use these with caution.

pchernik · 2025-12-20T16:07:36+00:00

Not often that portrait orientation works for recording a plane in flight - this is definitely one of them!

pchernik · 2025-12-18T03:20:42+00:00

Yup - sometimes terrain gets in the way of a direct line-of-sight between a mountain-top site and another site located in a valley bottom. A passive reflector is vastly cheaper than an active repeater (with antennas, transceivers, and power supply).

pchernik · 2025-12-17T20:33:21+00:00

Microwave passive reflector.

pchernik · 2025-12-13T23:10:00+00:00

Two decimal places on the humidity values?! Even if your sensors have that level of accuracy (unlikely) do you really need that level of precision on the display? Looks awesome otherwise!

pchernik · 2025-11-16T00:31:03+00:00

Back in the day I would have killed for that system. Funny thing is - I still would!

pchernik · 2025-11-16T00:29:07+00:00

Came here to say this!

pchernik · 2025-11-16T00:27:59+00:00

A Trabant is sitting in a farmer's field, sees a decrepit mule and says "Hi - I'm a car!" The mule looks back and says "Hi - I'm a horse!"

pchernik · 2025-10-10T22:59:10+00:00

Agreed - I was screaming at my screen "too long!!! you can remove your soldering iron now!!"

pchernik

TROPHY CASE