A (reasonably) accurate NES emulator with support for NROM/MMC3 games. Only runs on Linux with Vulkan-supported hardware.

NOTE: Game compatibility remains low. Only mappers 0 and 4 are supported, and ROM parsing is limited to INES-1.0. As of writing, many of the more obscure INES-header flags are simply ignored (including the presence of a trainer). Conveniences like user interface or interactive debugging have also not been prioritized - the primary focus of the project has been on the emulator core itself. Stability has likewise been low-priority, with me pushing directly to master and breaking things every other commit. Hopefully, however, the project can still serve as guidance for people wishing to make similar programs in Rust.

• mapper 0 and 4 support
• simple save states
• nearly cycle accurate (but not cycle-steppable) CPU emulation, including dummy reads/writes
• almost 8-cycle accurate PPU emulation
• low level emulation of MMC3 IRQ counter behavior

• APU emulation
• cycle accurate CPU NMI/IRQ polling
• dummy PPU nametable fetches at dots 337-340

.. and tons more

• instr_test_v5
  • 01-basics
  • 02-implied
  • 03-09 (unofficial opcodes aren't supported yet)
  • 10-branches
  • 11-stack
  • 12-jmp_jsr
  • 13-rts
  • 14-rti
  • 15-brk
  • 16-special
• instr_misc
  • 01-abs_x_wrap
  • 02-branch_wrap
  • 03-dummy_reads
  • 04-dummy_reads_apu (no apu emulation)
• instr_timing
  • 1-instr_timing (no apu emulation)
  • 2-branch_timing (no apu emulation)
• cpu_timing_test6
• branch_timing_tests
  • 1.Branch_Basics.nes
  • 2.Backward_Branch.nes
  • 3.Forward_Branch.nes
• ppu_vbl_nmi
  • 01-vbl_basics
  • 02-vbl_set_time
  • 03-vbl_clear_time
  • 04-nmi_control
  • 05-nmi_timing (no cycle accurate nmi polling)
  • 06-nmi_suppression
  • 07-nmi_on_timing (fails for unknown reasons - many other emulators seem to struggle with this one)
  • 08-nmi_off_timing
  • 09-even_odd_frames
  • 10-even_odd_timing (ppu cycle inaccuracies)
• ppu_sprite_overflow
  • 01-basics
  • 02-details
  • 03-timing (fails for reasons i've yet to investigate)
  • 04-obscure
  • 05 (haven't investigated this either)
• mmc3_test_2
  • 1-clocking
  • 2-details
  • 3-A12_clocking
  • 4-scanline_timing (ppu cycle inaccuracies)
  • 5-MMC3
  • 6-MMC3 (only newer MMC3 revisions are supported - both test 5 and 6 cannot pass at once)

to install, simply:

cargo install --path emulator/

run with:

nees [rom]

optionally:

nees [rom] --save [path/to/save/file]

Up/down/left/right are bound to WASD, A is bound to space, B is Shift, Select is F, and Start is Tab. Emulation can be paused by pressing Esc, stopped by pressing Ctrl+Q and saved by pressing P. Keybinds are currently not configurable (short of editing the source code).

• libxcb
• libxcb-keysyms
• xcb-util
• Vulkan SDK
• cargo

.. and related dev headers