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# RetroDream - RetroBIOS

Type | libretro
Classification | community_fork
Source | https://github.com/libretro/redream-next
Upstream | https://github.com/inolen/redream
Version | Git
Profiled | 2026-03-25
Cores | retrodream
Systems | sega-dreamcast

Technical notes

Fork of the last GPLv3 release of redream (inolen) before it went closed-source. The core has HLE bootstrap -- when boot.bin is missing, bios_invalid_instr() traps at PC=0x0 and calls bios_boot(), which loads IP.BIN and 1ST_READ.BIN directly from disc, sets up syscall vectors, and starts execution at 0xac008300.

The fork sets appdir to the RetroArch system directory root (retro_host.c:216-217), unlike the upstream which appends /dc (upstream retro_host.c:196-198). The .info still declares dc/ prefix paths matching the upstream, not this fork.

boot.bin is validated against four known MD5 hashes (boot.c:25-30). Validation failure logs a warning but the core continues via HLE.

flash.bin is read/write. If missing, bios_validate_flash() resets all partitions to defaults. Saved back to disk on shutdown (flash.c:197-199).

2 files | 0 required, 2 optional | 2 in repo, 0 missing | 1 with HLE fallback

`boot.bin` -optional, HLE available

- System: sega-dreamcast
- Size: 2.0 MB
- MD5: `['a5c6a00818f97c5e3e91569ee22416dc', '37c921eb47532cae8fb70e5d987ce91c', 'f2cd29d09f3e29984bcea22ab2e006fe', 'e10c53c2f8b90bab96ead2d368858623']`
- Validation: size, md5
- Source: `src/guest/rom/boot.c:12-80`
- Platforms: lakka, retroarch, retropie
- Dreamcast boot ROM. Four known variants accepted.

`flash.bin` -optional

- System: sega-dreamcast
- Size: 128.0 KB
- Validation: size
- Source: `src/guest/rom/flash.c:25-71`
- Platforms: lakka, retroarch, retrodeck, retropie
- Dreamcast flash memory. Written back on shutdown.

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