6502-emu

A cycle accurate 6502 emulator written in C++. Includes all official and unofficial opcodes. Passes nestest with correct cycle count, though it's not included in the tests here since the cartridge and memory mapping machinery both live in a WIP not-yet-public repo.

The goal here is to provide a flexible enough library frontent that 6502-emu could be reused in future emulations of complete 6502-based systems. I have an NES emulator in progress and hope to tackle C64 next.

Build it (with tests)

$ cd /path/to/6502-emu
$ ./build_dev.sh

Run the tests

Passes a number of test suites pulled from various forums including 6502.org user Klaus2m5's functional test suite.

$ cd build
$ ./test/catch

EhBASIC

NOTE: This is broken on account of some recent refactoring efforts in service of my NES project. Don't know when if ever I'll get around to fixing it up.

Implementation notes

This implementation is complete enough to be useful, I think, and performs reasonably well, executing the "Klaus Functional" test suite in ~0.6s (~160MHz, give or take).

TODO:

• Assemble and add interrupt test to catch suite.
• Memory mapping functionality (required for full-system emulation) is injected into the CPU at runtime and consumed via virtual function interface. I don't like the design of the mapper class very much.
• The instruction address mode decoding logic would probably be better implemented as straight lookup tables, both for performance reasons and for easier verification.