The Forth Deck mini: a portable Forth computer with a discrete CPU

The CPU for this computer is microcoded and is made out of a small number of discrete logic chips, plus an EEPROM. The data and address bus are 8 bits wide but the NOR unit operates on one bit only. The microcode has to loop in order to perform an 8 bit add.

I was looking for a hardware shifter in the diagram, because I figured it'd be necessary to access bits D1-D7. But there is none. He uses a lookup table in EEPROM to do the shift.

If you're interested in nice CPU designs, here's another one: the Novix NC4000 (also RTX2000), in which the bits in the instructions lead directly to control various muxes and units inside the chip. There's almost no decoding.

I have used to have an obsession with Forth and discrete CPUs when I was a teenager (if you google hard enough you will find an ancient webring of homebuilt CPUs out of discrete components), this obsession led me to my profession now - Digital Hardware Designer. My heart fills with joy when I see such posts at top of HN :) Great work!

I love reading about optimised Discrete CPUs like this.

Only 16 logic ICs. Doesn't even have an adder, the only ALU function is a 1 bit Nor gate.

Details on this page: http://mynor.org/my4th.htm

What's the modern day barrier to creating a "hobby" TRS-80 Model 100?

40x8 LCD display, one of the best keyboards ever made.

I see the custom keyboard community seem to be able to make any keyboard they like.

The keyboard on the Model 100 consumed the majority of its space, but at the same time, it was usable. I don't know what a reasonable display would be. The notable thing about the 40x8 is that it was big enough to be usable, and it was readable. I've seen some decks with tiny 640x480 displays, and they're not readable, particularly to my aging eyes.

The Psion 5 had a very usable keyboard, and better display than the M100. I don't know if that kind of keyboard can be made by a hobbyist like the other ones can. I don't know enough about keyboards. I don't know if one of those could be gutted and repurposed. (No doubt considered sacrilege to some.)

We see these "decks" with these matrices of buttons, but I'd dare say they're not really keyboards. The PET 2001 kind of proved that (and I did a lot of coding on a PET back in the day).

So, just curious what's stopping "real" ones, "nice" ones from showing up. I'd dare say money, but I see what folks spend money on for their hobbies, so it can't be that alone. Doesn't have to be a viable product for market.

I've built 5 of the author's My4th Light boards. Contact me (bio) if you're interested in one. I wouldn't mind building a batch of Forth Deck minis if people are interested too.

I plan to do a small demo video on Forth but haven't gotten around to it yet.

TL;DR: Looks like a step toward the AlphaSmart of programming

If you don't remember the AlphaSmart[1], it was a line of typewriter-like devices with small LCD displays. They ran on batteries for hours and had limited save space. You could hook them up to a larger computer to save your drafts.

Where's the programming version of that? The recent HN post[2] about running a Mac 128k on a RPI2040[3] got me thinking about that. In theory, you could get real work done on a system like that, although it wouldn't be very good for entertainment.

So, where's the AlphaSmart of low-power computing?

1. "Real" keyboard

2. Low-power display, ideally a larger e-ink one

3. Not connected to the internet

To be clear, I don't mean a TI-83-like[4], TI-92[5], or even the recent NumWorks[6]. Those are meant to be calculators and have inconvenient calculator-like form-factors.

[1]: https://en.wikipedia.org/wiki/AlphaSmart

[2]: https://news.ycombinator.com/item?id=40699684

[3]: https://axio.ms/projects/2024/06/16/MicroMac.html

[4]: https://en.wikipedia.org/wiki/TI-83_series

[5]: https://en.wikipedia.org/wiki/TI-92_series

[6]: https://www.numworks.com/

Some prior art in terms of computers with built-in Forth interpreters: https://en.wikipedia.org/wiki/Jupiter_Ace

And, of course, the Open Firmware used on Suns, PowerPC Macs, the One Laptop per Child, and others made use of Forth (including for the ROMs in expansion cards, allowing them to be CPU-agnostic): https://en.wikipedia.org/wiki/Open_Firmware

If you are into tiny computers but not especially moved by Forth or the prospect of soldering, you can get a rather capable ESP32 box for $30: https://shop.m5stack.com/products/m5stack-cardputer-kit-w-m5...

Hmmm... http://collapseos.org/forth.html

Reminds me about Oric-1

https://en.m.wikipedia.org/w/index.php?title=Oric_(computer)...

There’s implementation of Forth for Cardputter[0] if anyone is interested. I tried to boot it and it worked.

I’m not a Forth enthusiast myself but was thinking about doing something with Uiua, as I think it’s really fun toy language for such application.

[0]: https://github.com/ryu10/M5CardForth

woah, four lines display ? that's luxury. I remember coding on a single line display, kids these days...

What I'd love is a dialect of Factor written in Forth so that it could be run on these machines. Factor is a much higher-level Forth that is usable for scripting. Would make it more fun to use.

Oh, this is _nice_! It's not quite what I'd want, but all the schematics and software is there, so it wouldn't be too hard to change things to taste. :)

What is this exactly? What do you do with it?

how much does this cost?

The Parallax Propeller 2 comes with this by default, check it out.