// the find
jdah/jdh-8
An 8-bit minicomputer with a fully custom architecture
A from-scratch 8-bit computer with a custom 16-instruction RISC ISA, implemented in Logisim and built physically on breadboards. Comes with an assembler, emulator, a tiny OS, and programs including Pong. This is a personal project documented on YouTube, not a framework or library — you're here to learn from it or be inspired by it.
The ISA is cleanly designed: 8 general-purpose registers with dual roles (H/L as indirect address pair), a minimal but complete instruction set that can express real programs. The assembler supports macros, which saves you from the misery of raw hand-assembly. The emulator has a loadable module system for devices, so you can attach virtual hardware without hacking the core. The included programs (Pong, a holiday demo) prove the architecture actually works end-to-end, not just in theory.
Abandoned since June 2022 — the schematic requires a patched fork of Logisim Evolution that you have to build from source, and there's no guarantee that fork is maintained either. No unconditional jump instruction; JNZ with HL as the target means you always need HL loaded for jumps, which is an awkward constraint once you start writing non-trivial control flow. The OS is more of a sketch — `os.asm` and `oscall.asm` exist but there's no documentation on what syscalls are available or how they're called. Windows build setup is genuinely painful (six manual steps, a SourceForge download for xxd).