puNES - RetroBIOS¶
Technical notes
Qt emulator of the NES, the Famicom and the Family Computer Disk System, also playing NSF and NSFE music files. A cartridge boots with nothing supplied: the 2A03, the PPU and every mapper are emulated in software.
Four names are fixed by the code. disksys.rom and gamegenie.rom share one four-step lookup (src/core/fds.c:265-309, src/core/cheat.c:74-108): the path recorded in the configuration, the working directory, the directory holding the loaded image, then the bios folder of the data directory. nes20db.xml and dip.cfg are read from the XDG data directories under a puNES subdirectory, then the base of the data directory, then the application directory (src/gui/nes20db.cpp:50-79, src/gui/dipswitch.cpp:61-85); the installer writes both into the shared data directory (CMakeLists.txt:227-228).
The data directory is the application directory under --portable, %APPDATA%/puNES on Windows and ~/.local/share/puNES elsewhere (src/gui/qt.cpp:561-575), so the bios folder is ~/.local/share/puNES/bios.
No length and no hash is ever compared. fds_load_bios computes a CRC32 of the BIOS it loaded (src/core/fds.c:329) and the only reader of that value is the log line at src/core/fds.c:502-503.
The iNES 1.0 game database is compiled in as src/core/database.h and carries
the Vs. System PPU type and the region, so Vs. System titles need no
external file. The uPD7756 ADPCM samples of mappers 018, 086 and 072 come
from the Misc ROM area of the NES 2.0 dump itself
(src/core/mappers/mapper_018.c:51, mapper_086.c:56, mapper_072.c:45).
loadWaveFiles, which would read /samples/
Palettes, shaders, cheat imports and soft patches are opened from paths the user picks in a file dialog and no name is fixed by the code, so they carry no file entry here. A palette shorter than 192 bytes is refused and a built-in table is used instead (src/core/palette.c:39-64, src/video/gfx.c:323-334).
4 files | 1 required, 3 optional | 4 in repo, 0 missing
disksys.rom required in repo
Family Computer Disk System BIOS
- System: nintendo-fds
- Size: 8.0 KB
- Source:
src/core/fds.c:34,src/core/fds.c:259-332,src/core/fds.c:191-193,src/core/mappers/mapper_FDS.c:81 - Platforms: batocera, emudeck, lakka, recalbox, retroarch, retrobat, retrodeck, retropie, romm
- 8192 bytes are read into PRG ROM and mapped at 0xE000. When none of the four locations holds the file, fds_load_bios logs FDS;bios not found and returns EXIT_ERROR, which the caller propagates, so the disk image does not load. A short read only logs FDS;error on reading bios.
gamegenie.rom optional in repo
Game Genie ROM, booted in place of the cartridge to reach the code entry screen
- System: nintendo-nes
- Source:
src/core/cheat.c:30,src/core/cheat.c:69-120,src/core/cheat.c:121-179,src/core/ines.c:97-99 - Loaded only while the cheat mode is set to Game Genie. The whole file is read, its length taken from the file itself. Absent, gamegenie_load_rom returns early and the cartridge boots directly.
nes20db.xml optional in repo
NES 2.0 header database, matched by ROM hash
- System: nintendo-nes
- Source:
src/gui/nes20db.cpp:31,src/gui/nes20db.cpp:49-81,src/core/ines.c:276-278,src/core/unif.c:316,CMakeLists.txt:227 - Supplies mapper, submapper, mirroring, region, RAM sizes and Vs. System hardware for dumps whose own header is absent or wrong. A miss leaves info.mapper.nes20db.in_use false and the header carried by the ROM is used.
dip.cfg optional in repo
DIP switch database for multicart and Vs. System boards, keyed by CRC32
- System: nintendo-nes
- Source:
src/gui/dipswitch.cpp:30,src/gui/dipswitch.cpp:60-86,src/core/mappers.c:44,CMakeLists.txt:228 - Read on every mapper init. A miss leaves dipswitch.used false, which mappers 001, 043, 045, 176, 215, 412 and 447 and the selection dialog at src/gui/qt.cpp:754 all guard on, so the board runs on its reset value.
Generated on 2026-08-23T16:12:06Z