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# DirectXBox - RetroBIOS

Type | libretro
Classification | pure_libretro
Source | https://github.com/libretro/libretro-directxbox
Version | alpha
Profiled | 2026-03-23
Cores | directxbox
Systems | xbox

2 files | 2 required, 0 optional | 2 in repo, 0 missing

`mcpx_1.0.bin` -required

- Size: 512 B
- Validation: size
- Source: `src/xbox.cpp:186-207, src/libretro/libretro.cpp:202`
- Platforms: batocera, emudeck, recalbox, retrobat, retrodeck
- Xbox MCPX ROM (secret boot ROM on the southbridge). Contains the initial boot vector that loads the flash BIOS. Overlaid at the last 512 bytes of the 16 MB flash region (0xFFFFFE00-0xFFFFFFFF). Only needed for retail machine types; Debug and Chihiro skip this file.

`cromwell_1024.bin` -required

- Validation: size
- Source: `src/xbox.cpp:143-178, src/libretro/libretro.cpp:203`
- Cromwell open-source Xbox BIOS (1024 KB variant). Loaded as the flash ROM and mirrored across the 16 MB flash region at 0xFF000000. Size must be a multiple of 0x10000. This is the only BIOS that currently boots in the emulator. The Microsoft retail BIOS (xbox-3944.bin) is referenced in commented-out code but does not work yet.

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