emulator: IroGB
type: libretro
core_classification: official_port
source: "https://github.com/AlexSutila/IroGB"
upstream: "https://github.com/AlexSutila/IroGB"
profiled_date: "2026-09-03"
source_commit: "7b6bb9b1f9cbf04e49eea0dc89c54635c2b54056"
core_version: "1.0.0"
display_name: "Nintendo - Game Boy / Color (IroGB)"
cores:
  - irogb
systems:
  - nintendo-gb
  - nintendo-gbc

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.

files:
  - name: "dmg_boot.bin"
    system: nintendo-gb
    description: "Game Boy (DMG) boot ROM"
    required: false
    hle_fallback: true
    size: 256
    validation: [size]
    source_ref: "src/frontend/libretro/libretro_host.cpp:91, src/frontend/libretro/libretro_host.cpp:106, src/frontend/libretro/libretro_host.cpp:61-84, src/memory/boot.cpp:10-24"
    note: "Opened with irogb_bios set to dmg, or to auto when cgb_boot.bin is absent."

  - name: "cgb_boot.bin"
    system: nintendo-gbc
    description: "Game Boy Color (CGB) boot ROM"
    required: false
    hle_fallback: true
    size: 2304
    validation: [size]
    source_ref: "src/frontend/libretro/libretro_host.cpp:97, src/frontend/libretro/libretro_host.cpp:104, src/frontend/libretro/libretro_host.cpp:61-84, src/memory/boot.cpp:10-24, src/gbc.cpp:330-340"
    note: "Opened with irogb_bios set to cgb or auto. Under auto it also boots DMG cartridges in CGB mode."