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Beetle PSX (Mednafen PSX) - RetroBIOS
Type libretro
Classification Community forks
Source https://github.com/libretro/beetle-psx-libretro
Upstream https://mednafen.github.io/
Version v0.9.44.1
Profiled 2026-03-29
Cores beetle_psx, mednafen_psx, mednafen_psx_hw
Systems sony-playstation
Technical notes

Region-based BIOS selection: the core picks JP/NA/EU firmware based on disc region. SHA1 validated with warning on mismatch (does not block loading). SHA1 and alternate filenames sourced from MAME (mame src/mame/sony/psx.cpp); the lists and the checksum search live in libretro.c:388-442,450-542. Override option allows using PSP, PS3, or OpenBIOS as region-free alternative. Embedded OpenBIOS (512KB) compiled into the binary serves as HLE fallback when no BIOS found. "Skip BIOS" option patches BIOS ROM but causes compatibility issues. Upstream Mednafen loads the same 3 region BIOS; override BIOS and HLE fallback are libretro additions. Two BIOS geometries are accepted: the stock 512 KB kernel and the 1 MB SCPH-5903 part, selected by file size at load time (libretro.c:3297-3311). A 1 MB image switches Video CD from HLE to daughterboard emulation (libretro.c:6229). Reached through the BIOS path override only: the region name lists carry no SCPH-5903 entry, and the firmware scan compares against the region SHA1, so a 1 MB file never matches there (libretro.c:425-433). Mednafen rejects a BIOS that is not 524288 bytes (mednafen psx.cpp:1777), and the fork keeps that geometry as BIOS_SIZE_STD (libretro.c:1226), so this geometry is libretro only.

7 files | 3 required, 4 optional | 7 in repo, 0 missing | 3 with HLE fallback

scph5500.bin required in repo HLE fallback both japan
SCPH-5500 (v3.0 09-09-96 J)

scph5903.bin optional in repo libretro japan
SCPH-5903 (System ROM Version 2.2 12/04/95 J), Video CD daughterboard

scph5501.bin required in repo HLE fallback both north-america
SCPH-5501, 5503, 7003 (v3.0 11-18-96 A)

scph5502.bin required in repo HLE fallback both europe
SCPH-5502, 5552 (v3.0 01-06-97 E)

psxonpsp660.bin optional in repo libretro world
PSP embedded PS1 BIOS (region-free override)

ps1_rom.bin optional in repo libretro world
PS3 embedded PS1 BIOS, first 512KB extracted (region-free override)

openbios.bin optional in repo libretro world
OpenBIOS (open-source PS1 HLE BIOS, region-free override)

  • Size: 512.0 KB
  • Aliases: OPENBIOS.bin
  • Source: libretro.c:479-485
  • override_bios=3. No SHA1 validation. Falls back to region BIOS if not found. Also embedded in binary as HLE fallback (libretro.c:2358-2360).

Generated on 2026-09-14T09:03:09Z