6502

Files about the 6502 CPU family (6502, 6507, 2A03) and software written for it.

• Game Annotation Series — documenting classic game source at the system level; meta-stress-test for LLM interpretation of low-level code
• TIA Reference — Television Interface Adaptor specs; 6507’s role in beam-racing
• PPU Reference — Ricoh 2C02; registers, NMI timing, OAM, scrolling, VBlank window
• APU Reference — 5-channel audio with autonomous envelope/sweep/length-counter
• Mappers Reference — NROM, MMC1, MMC3, etc.; cartridge logic that scales the platform
• NES Research — platform overview; 2A03 vs 6507 comparison; storytelling-vs-logic axis
• Battlezone (1980) — 3D Without a Multiply Instruction — the 6502’s missing MUL/DIV as a design constraint: every real multiply offloaded to a 2901 coprocessor; shifts, CMP #$80/ROR arithmetic-shift-right, and table lookup are all the CPU keeps
• Arithmetic Scarcity and the 3D Problem — the 6502’s missing MUL/DIV placed on the wider curve: PDP-8 EAE → PDP-11 EIS → 8087 → integrated FPU; fast math as a purchasing decision for three decades
• Stellar 7 (1983) — The Same Game Without the Coprocessor — what 6502 software arithmetic actually costs: a 695-byte Divide16 and a fully-unrolled signed 16×8 multiply, the routines Battlezone contains none of
• Arithmetic as a Purchase — Sixty Years of Paying for Multiply — the 8-bit era as a regression: the 6502 could do less arithmetic than a 1959 mainframe or a 1966 spacecraft, because every cheaper substrate loses the capability and has to re-earn it
• Bandit Kings of Ancient China (NES) — Game 6 in the KOEI NES decompiler family — decompile order, not release order.
• Gemfire (NES, 1992) — Game 7 in the KOEI NES decompiler family (decompile order, not release order — L’Empereur is
• Genghis Khan (NES) — Design clock 1987; Famicom port 1989-04-20.
• KOEI tools — the shared engine toolchain — Tools node, not a title index. One studio, one bytecode-VM engine lineage, two consoles.
• L’Empereur (NES, 1991) — Game 8 in the KOEI NES decompiler family.
• LADS — byte-exact reconstruction — A reconstruction of LADS, the memory-resident 6502 assembler from Richard Mansfield’s
• Lowering Atlas — Sibling tooling to the NA1 decompiler, in the same repo: compile known C control-flow
• NA1 — Nobunaga’s Ambition (NES) — The bytecode-VM decompiler that outgrew annotation and became the series’ crucible.
• NES / Famicom — system node — The 6502 + PPU substrate and every title decompiled on it.
• NES system tools — rendering & emulator integration — The target-agnostic NES tooling: rendering, and Mesen (emulator) integration.
• ROTK1 — Sangokushi (NES) — The earliest title in the KOEI NES decompiler family, and the baseline the other four are read
• ROTK2 — Sangokushi II (NES) — Design clock 1989; Famicom port 1990.
• The comparison studies — paired deep-reads — The four titles the series started as, organized in paired comparisons.