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IroGB - RetroBIOS
Type libretro
Classification Official ports
Source https://github.com/AlexSutila/IroGB
Version 1.0.0
Profiled 2026-09-03
Cores irogb
Systems nintendo-gb, nintendo-gbc
Technical notes

IroGB is a Game Boy and Game Boy Color emulator by Alex Sutila. The libretro frontend lives in src/frontend/libretro of the same repository as the SDL3, raylib and Python frontends. The buildbot builds the repository default branch, release, with cmake -DBUILD_LIBRETRO=ON -DNO_CORE_FILESYSTEM=ON (.gitlab-ci.yml:10-14).

Boot ROMs are read from the root of the system directory (src/frontend/libretro/libretro_host.cpp:61-84). The irogb_bios core option picks the file: dmg opens dmg_boot.bin, cgb opens cgb_boot.bin, auto (the default) tries cgb_boot.bin then dmg_boot.bin, none opens nothing (src/frontend/libretro/libretro_host.cpp:86-113). Under auto a DMG cartridge boots through the CGB boot ROM whenever cgb_boot.bin is present and gets the CGB colouring of monochrome games; the irogb_monochrome_dmg option turns that off.

BootROM accepts a file of exactly 256 or 2304 bytes and rejects any other size (src/memory/boot.cpp:10-24). The size also picks the machine: a 2304-byte image starts in CGB mode (src/gbc.cpp:330-340). 256 bytes covers DMG, DMG0, MGB and SGB dumps, 2304 bytes CGB, CGB0, AGB0 and AGB dumps (includes/memory/boot.hpp:9-30); only the two names above are ever opened. No hash is checked.

Without a boot ROM, or when the file fails to open or has another size, the core continues with skip_bios(), which loads post-boot CPU and MMIO values, unmaps the boot ROM and sets CGB mode from the cartridge header (src/gbc.cpp:342-349, src/gbc.cpp:387-405, src/gbc.cpp:489-490).

The .info declares cgb_bios.bin; the code opens cgb_boot.bin.

2 files | 0 required, 2 optional | 2 in repo, 0 missing | 2 with HLE fallback

dmg_boot.bin optional in repo HLE fallback
Game Boy (DMG) boot ROM

cgb_boot.bin optional in repo HLE fallback
Game Boy Color (CGB) boot ROM

Generated on 2026-09-14T09:03:10Z