CFM: the Cliffle Forth Machine

This is a Forth-inspired processor targeting the Lattice ICE40 FPGA series, primarily targeting the Icoboard.

The CFM core is designed for high performance (40+ MHz) on the ICE40 HX grade parts. It is written in Haskell and synthesized using Clash. Because the Haskell expression of the circuit is directly executable, we also have a cycle-accurate emulator "for free."

The distribution includes BsForth, a non-ANS Forth implementation that can provide a bare-bones interactive development environment with optimizing compiler in less than 5 kiB. It's interesting in the way that it bootstraps (using the cycle-accurate emulator) and for its machine instruction fusion algorithm.

More reading:

• Docs on the instruction set and programmer's model
• The interrupt model
• The Icoboard demo
• The Icestick demo
• Self-hosting: how to recompile BsForth from within BsForth, without using a separate computer.