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RetroForth 2021.1 Is Released
6 projects | news.ycombinator.com | 17 Feb 2021
If you’re into this you may also like durex forth: https://github.com/jkotlinski/durexforth
A modern C64 variant, as well as CollapseOS which is a Forth based 8-bit OS: https://collapseos.org/
FPGAs for interpreted programming languages?
2 projects | /r/FPGA | 25 Nov 2022
How many LUT for an 8 bit CPU?
2 projects | /r/FPGA | 11 Nov 2022
Thanks! Found the port of this to the board I want :) https://github.com/jamesbowman/swapforth/tree/master/j1a
The RISC Deprogrammer
2 projects | news.ycombinator.com | 28 Oct 2022
It's a standard thing to do in EE curricula; you normally do it in a one-semester class, and there are literally thousands of open-source synthesizable CPU cores on GitHub now.
To take two examples to show that designing a CPU is less work than writing a novel:
- Chuck Thacker's "A Tiny Computer", fairly similar to the Nova, is a page and a half of synthesizable Verilog; it runs at 66 MHz in 200 LUTs of a Virtex-5: https://www.cl.cam.ac.uk/~swm11/examples/bluespec/Tiny3/Thac...
- James Bowman's J1A is more like Chuck Moore's MuP21 and is about three pages of synthesizable Verilog: https://github.com/jamesbowman/swapforth/blob/master/j1a/ver... and https://github.com/jamesbowman/swapforth/blob/master/j1a/ver.... You can build it with Claire Wolf's iCEStorm (yosys, etc.) and run it on any but Lattice's tiniest FPGAs; it takes up 1162 4-input LUTs.
I haven't quite done it myself. Last time I played https://nandgame.com/ it took me a couple of hours to play through the hardware design levels. But that's not really "design" in the sense of defining the instruction set (which is also kind of Nova-like), thinking through state machine design, and trying different pipeline depths; you're mostly just doing the kind of logic minimization exercises you'd normally delegate to yosys.
In https://github.com/kragen/calculusvaporis I designed a CPU instruction set, wrote a simulator for it, wrote and tested some simple programs, designed a CPU at the RTL level, and sketched out gate-level logic designs to get an estimate of how big it would be. But I haven't simulated the RTL to verify it, written it down in an HDL, or breadboarded the circuit, so I'm reluctant to say that this qualifies as "designing a single CPU" either.
What are some alternatives?
zeptoforth - A not-so-small Forth for Cortex-M
arkam - A Simple Stack VM and Forth
factor - Factor programming language
jonesforth - Mirror of JONESFORTH
gforth - Gforth mirror on GitHub (original is on Savannah)
subleq - 16-bit SUBLEQ CPU running eForth - just for fun
stoneknifeforth - a tiny self-hosted Forth implementation
elfort - A Forth metacompiler that directly emits an executable binary for x86-64 Linux written in Arkam
lbForth - Self-hosting metacompiled Forth, bootstrapping from a few lines of C; targets Linux, Windows, ARM, RISC-V, 68000, PDP-11, asm.js.
gforth-raylib - Raylib 3.5 bindings for Gforth. The name is backwards for obvious reasons.