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Flycast 2021
Type libretro
Classification Frozen snapshots
Source https://github.com/metallic77/flycast
Upstream https://github.com/libretro/flycast
Version 0.1
Revision metallic77/flycast@603814c9f73b, libretro/flycast@4c293f306bc1
Profiled 2026-10-17
Profile YAML, JSON
Cores flycast2021
Systems sega-dreamcast, sega-naomi, sega-atomiswave
Technical notes

The libretro/flycast tree as of April 2022 (merge base 4c293f30), from before the libretro fork was rebased on flyinghead's Flycast, with 22 commits by metallic77 on top that tune defaults and build flags for low-end handhelds. ROCKNIX renames the core option prefix from reicast to flycast2021 and installs the library as flycast2021_libretro.so. ref: core/libretro/libretro.cpp:2296-2300

Every system file lives in <system>/dc/. ref: core/libretro/libretro.cpp:1893-1896

Dreamcast: the boot ROM is looked for as dc_boot.bin, dc_boot.bin.bin, dc_bios.bin, dc_bios.bin.bin, the first that yields a full 2 MB read wins. The HLE BIOS core option (hle_bios) defaults to enabled, and when it is on, or when no boot ROM loads, reios boots the disc instead. Booting to the BIOS menu, or starting without a disc, needs the real boot ROM and fails with -3 without it. ref: core/hw/holly/sb_mem.cpp:32-65, core/hw/holly/sb_mem.cpp:215-233, core/hw/flashrom/flashrom.h:54-67, core/hw/flashrom/flashrom.h:84-118, core/nullDC.cpp:420-431, core/nullDC.cpp:455-463, core/libretro/libretro_core_options.h:133-145, core/libretro/libretro.cpp:726-731

NAOMI and Atomiswave: a BIOS archive is opened as <system>/dc/<name> with .7z then .zip appended. Each member is looked for in the game archive, its parent, then the BIOS archive, by CRC32 and then by name. The BIOS table carries no CRC32, so only the name matches. The member for the configured region is tried first, then the first member listed. A game whose table entry names a BIOS refuses to start without it, and the others default to naomi. Five archive names are reachable from the game table: naomi, awbios, f355bios, f355dlx, hod2bios. airlbios and naomigd have table entries but no game names them. ref: core/hw/naomi/naomi_cart.cpp:76-176, core/hw/naomi/naomi_cart.cpp:227-247, core/archive/archive.cpp:26-42, core/hw/naomi/naomi_roms.h:76-217

LoadRomFiles also reads naomi_boot.bin, naomi_boot.bin.bin, naomi_bios.bin, naomi_bios.bin.bin and epr-21576d.bin for NAOMI, but naomi_cart_Close clears bios_loaded before the cartridge loads, so that file never stands in for naomi.zip. ref: core/hw/holly/sb_mem.cpp:59, core/hw/naomi/naomi_cart.cpp:427-444, core/hw/naomi/naomi_cart.cpp:472-484

8 files | 5 required, 3 optional | 8 in repo, 0 missing | 1 with HLE fallback Categories: 3 BIOS, 5 BIOS ZIPs

dc_boot.bin optional in repo HLE fallback #
Dreamcast boot ROM

  • Path: dc/dc_boot.bin
  • System: sega-dreamcast
  • Size: min 2.0 MB
  • Aliases: dc_boot.bin.bin, dc_bios.bin, dc_bios.bin.bin
  • Validation: size
  • Source: core/hw/holly/sb_mem.cpp:50-65, core/hw/holly/sb_mem.cpp:215-229, core/hw/flashrom/flashrom.h:54-67, core/nullDC.cpp:420-431
  • Collection copy: bios/Sega/Dreamcast/dc_bios.bin
  • Platforms: batocera dc/dc_boot.bin, emudeck dc/dc_boot.bin, lakka dc/boot.bin, dc/dc_boot.bin, recalbox dc/dc_boot.bin, retroarch dc/boot.bin, dc/dc_boot.bin, retrobat dc/dc_boot.bin, retrodeck bios/dc/dc_boot.bin, retropie dc/boot.bin, dc/dc_boot.bin, rocknix dc/dc_boot.bin, romm dc/boot.bin, dc/dc_boot.bin
  • Read as 2 MB into the system ROM, and a shorter file is rejected. Needed only to boot to the BIOS menu or when the HLE BIOS option is disabled.

dc_nvmem.bin optional in repo #
Dreamcast flash ROM

  • Path: dc/dc_nvmem.bin
  • System: sega-dreamcast
  • Size: min 128.0 KB
  • Aliases: dc_flash_wb.bin, dc_flash.bin, dc_flash.bin.bin
  • Validation: size
  • Source: core/hw/holly/sb_mem.cpp:196-213, core/hw/holly/sb_mem.cpp:231, core/hw/holly/sb_mem.cpp:236-243, core/hw/holly/sb_mem.cpp:271-278
  • Collection copy: bios/Sega/Dreamcast/dc_nvmem.bin
  • Loaded with the boot ROM and by the HLE path. A missing file leaves the flash blank and the core runs. Written back as dc_nvmem.bin.

font.bin optional in repo #
Dreamcast system font for the HLE BIOS

  • Path: dc/font.bin
  • System: sega-dreamcast
  • Source: core/reios/reios.cpp:736-755
  • Collection copy: bios/Sega/Dreamcast/font.bin
  • Read whole into the font table of the reios ROM image. Absent, a built-in font is copied there.

naomi.zip required in repo bios_zip #
NAOMI BIOS archive

  • Path: dc/naomi.zip
  • System: sega-naomi
  • Source: core/hw/naomi/naomi_roms.h:132-189, core/hw/naomi/naomi_cart.cpp:227-247, core/hw/naomi/naomi_cart.cpp:472-484
  • Collection copy: bios/Arcade/Arcade/naomi.zip
  • Platforms: recalbox dc/naomi.zip
  • Default BIOS of every NAOMI game whose table entry names none, cartridge, .lst, .bin and .dat images alike. One member is loaded: the one for the configured region, else epr-21576h.ic27.
  • Contents (4 members):
    • epr-21576h.ic27: Japan, 2.0 MB
    • epr-21578h.ic27: Export, 2.0 MB
    • epr-21577h.ic27: USA, 2.0 MB
    • epr-21579d.ic27: Korea, 2.0 MB

awbios.zip required in repo bios_zip #
Atomiswave BIOS archive

  • Path: dc/awbios.zip
  • System: sega-atomiswave
  • Source: core/hw/naomi/naomi_roms.h:86-94, core/hw/naomi/naomi_cart.cpp:89-92, core/hw/naomi/naomi_cart.cpp:171-173
  • Collection copy: bios/Arcade/Arcade/awbios.zip
  • Platforms: batocera dc/awbios.zip, lakka dc/awbios.zip, recalbox dc/awbios.zip, retroarch dc/awbios.zip, retrodeck bios/awbios.zip, bios/dc/awbios.zip, retropie dc/awbios.zip, romm arcade/awbios.zip
  • Named by all 34 Atomiswave games. Loaded into the flash chip, whose writable part is then reloaded from the save directory.
  • Contents (1 members):
    • bios0.ic23: 128.0 KB

f355bios.zip required in repo bios_zip #
Ferrari F355 Challenge BIOS archive

  • Path: dc/f355bios.zip
  • System: sega-naomi
  • Source: core/hw/naomi/naomi_roms.h:95-103, core/hw/naomi/naomi_cart.cpp:238-243
  • Collection copy: bios/Arcade/Arcade/f355bios.zip
  • Platforms: lakka dc/f355bios.zip, retroarch dc/f355bios.zip, retrodeck bios/dc/f355bios.zip, bios/f355bios.zip, retropie dc/f355bios.zip, romm arcade/f355bios.zip
  • Named by three Ferrari F355 Challenge entries, which refuse to start without it.
  • Contents (3 members):
    • epr-22851.ic27: Export, 2.0 MB
    • epr-22850.ic27: USA, 2.0 MB
    • epr-22849.ic27: Japan, 2.0 MB

f355dlx.zip required in repo bios_zip #
Ferrari F355 Challenge Deluxe BIOS archive

  • Path: dc/f355dlx.zip
  • System: sega-naomi
  • Source: core/hw/naomi/naomi_roms.h:104-119, core/hw/naomi/naomi_roms.h:1701, core/hw/naomi/naomi_cart.cpp:238-243
  • Collection copy: bios/Arcade/Arcade/f355dlx.zip
  • Platforms: lakka dc/f355dlx.zip, retroarch dc/f355dlx.zip, retrodeck bios/dc/f355dlx.zip, bios/f355dlx.zip, retropie dc/f355dlx.zip, romm arcade/f355dlx.zip
  • Named by the f355 entry, which refuses to start without it.
  • Contents (3 members):
    • epr-21864.ic27: Export, 2.0 MB
    • epr-21863.ic27: USA, 2.0 MB
    • epr-21862.ic27: Japan, 2.0 MB

hod2bios.zip required in repo bios_zip #
The House of the Dead 2 BIOS archive

  • Path: dc/hod2bios.zip
  • System: sega-naomi
  • Source: core/hw/naomi/naomi_roms.h:120-131, core/hw/naomi/naomi_cart.cpp:238-243
  • Collection copy: bios/Arcade/MAME/hod2bios.zip
  • Named by four House of the Dead 2 entries, which refuse to start without it.
  • Contents (3 members):
    • epr-21331.ic27: Export, 2.0 MB
    • epr-21330.ic27: USA, 2.0 MB
    • epr-21329.ic27: Japan, 2.0 MB

Generated on 2026-10-20T03:49:41Z