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# b2 - RetroBIOS

Type | standalone + libretro
Classification | community_fork
Source | https://github.com/zoltanvb/b2-libretro
Upstream | https://github.com/tom-seddon/b2
Version | v0.4
Profiled | 2026-03-23
Cores | b2
Systems | bbc-micro-b, bbc-micro-bplus, bbc-master-128

Technical notes

Libretro port by Zoltan Balogh of Tom Seddon's b2 BBC Micro emulator. is_experimental=true in .info. ref: zoltanvb/b2-libretro, tom-seddon/b2

Standalone loads ROMs from etc/roms/ via GetAssetPath() + LoadFile(). ref: tom-seddon/b2/src/b2/roms.cpp:9-10

Libretro port embeds all ROMs as hex arrays in src/libretro/roms.hpp. create_core() loads OS and sideways ROMs from static machine_types[] arrays. GetAssetPath() and LoadFile() are stubbed — no file I/O at runtime. ref: zoltanvb/b2-libretro/src/libretro/roms.hpp ref: zoltanvb/b2-libretro/src/libretro/core.cpp:274-304 ref: zoltanvb/b2-libretro/src/libretro/adapters.cpp:74-78

9 machine types: B/Acorn 1770, B/Watford DDB2, B/Watford DDB3, B/Opus 1770, B/Opus Challenger 256K, B/Opus Challenger 512K, B+, B+128, Master 128 (MOS 3.20). Master 3.50, Master Turbo, Master Compact not yet implemented. ref: zoltanvb/b2-libretro/src/libretro/core.h:117

No BIOS or firmware files required. Generated on 2026-03-25T14:56:43Z