Skip to content

mGBA - RetroBIOS
Type libretro
Classification official_port
Source https://github.com/libretro/mgba
Upstream https://github.com/mgba-emu/mgba
Version 0.10-dev
Profiled 2026-03-24
Cores mgba
Systems nintendo-gba, nintendo-gb, nintendo-gbc, nintendo-sgb
Platform details

gba: - bios_size: 16384 - hle_bios: True - source_ref: src/gba/hle-bios.c, src/gba/gba.c:520-551 - notes: GBALoadBIOS() validates size (must be exactly 0x4000) then computes

an internal checksum. Two official checksums are recognized: GBA_BIOS_CHECKSUM = 0xBAAE187F (standard GBA) GBA_DS_BIOS_CHECKSUM = 0xBAAE1880 (DS GBA mode) Other checksums trigger a warning but the file is still loaded.

**gb:**
- bios_size: 256
- hle_bios: False
- source_ref: src/gb/gb.c:570-605
- notes: GBIsBIOS() validates by CRC32. Accepted DMG-family checksums:

DMG0 = 0xC2F5CC97, DMG = 0x59C8598E, MGB = 0xE6920754 Files not matching any known checksum are rejected.

**gbc:**
- bios_size: 2304
- hle_bios: False
- source_ref: src/gb/gb.c:570-605
- notes: Accepted CGB-family CRC32 checksums:

CGB = 0x41884E46, CGB0 = 0xE8EF5318, CGBE = 0xE95DC95D AGB = 0xFFD6B0F1, AGB0 = 0x570337EA

**sgb:**
- bios_size: 256
- hle_bios: False
- source_ref: src/gb/gb.c:570-605, src/gb/core.c:642-644
- notes: Accepted SGB CRC32 checksums:

SGB = 0xEC8A83B9, SGB2 = 0x53D0DD63 SGB2 maps here in standalone (marked TODO upstream). Libretro port omits SGB2 case, falls to gb_bios.bin.

Technical notes

mGBA is a Game Boy Advance emulator with Game Boy, Game Boy Color, and Super Game Boy support.

All BIOS files are optional. mGBA ships a built-in HLE BIOS for GBA (src/gba/hle-bios.c) that covers most software. The real BIOS improves accuracy (startup logo, some edge-case SWI behavior). There is no HLE BIOS for GB/GBC/SGB -- those rely on GBSkipBIOS() if no file is found.

BIOS loading is controlled by two core options: mgba_use_bios (default ON) - whether to look for BIOS files at all mgba_skip_bios (default OFF) - skip the boot animation even if loaded

The libretro port resolves BIOS filenames in retro_load_game() (src/platform/libretro/libretro.c:2091-2148). It picks the filename based on detected model: GBA -> gba_bios.bin GB (DMG/MGB) -> gb_bios.bin GBC (CGB/AGB) -> gbc_bios.bin SGB -> sgb_bios.bin SGB2 -> gb_bios.bin (falls to default, missing case)

The standalone core (src/gb/core.c:637-684) correctly maps SGB2 to sgb_bios.bin (marked TODO for a dedicated file). The libretro port omits GB_MODEL_SGB2 from its switch, so SGB2 falls to default.

GBIsBIOS() in src/gb/gb.c validates BIOS files by CRC32 checksum. Accepted checksums cover DMG, DMG0, MGB, SGB, SGB2, CGB, CGB0, CGBE, AGB, and AGB0 revisions.

4 files | 0 required, 4 optional | 4 in repo, 0 missing | 1 with HLE fallback

gba_bios.bin -optional, HLE available

gb_bios.bin -optional

gbc_bios.bin -optional

sgb_bios.bin -optional

Generated on 2026-03-25T14:56:43Z