Add support for undocumented (illegal) 6502 opcodes.
Motivation: Many retro demos, games, and cracking tools rely on illegal opcodes. Supporting them is a differentiator for emulators and required for running real-world C64/NES software.
Scope:
- Implement the ~105 unofficial opcodes (LAX, SAX, DCP, ISC, SLO, RLE, SRE, ANC, ALR, ARR, SBX, etc.)
- Add an --illegal-opcodes\ flag (or --cpu nmos6502-undoc) to enable them
- Assembler support: recognize illegal mnemonics when the flag is set
- Tom Harte's SingleStepTests include vectors for illegal opcodes — validate against them
Priority: High — strong community demand, good test coverage already available.
Add support for undocumented (illegal) 6502 opcodes.
Motivation: Many retro demos, games, and cracking tools rely on illegal opcodes. Supporting them is a differentiator for emulators and required for running real-world C64/NES software.
Scope:
Priority: High — strong community demand, good test coverage already available.