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# EmuSCV - RetroBIOS

Type | libretro
Classification | community_fork
Source | https://github.com/wzcwzc/emuscv
Upstream | http://takeda-toshiya.my.coocan.jp/
Version | 0.12
Profiled | 2026-03-23
Cores | emuscv
Systems | scv

Platform details

cpu: NEC UPD7801G bios_mapping: - upd7801g: {'target': '0x0000-0x0FFF (CPU internal ROM, 4 KB)', 'format': 'raw binary', 'source_ref': 'src/vm/scv/memory.cpp:249-254', 'notes': 'Memory map from memory.cpp:initialize():\n 0x0000-0x0FFF BIOS ROM (read-only)\n 0x2000-0x3FFF VRAM (8 KB)\n 0x8000-0xFF7F Cartridge ROM (up to 4 banks of 32 KB)\n 0xFF80-0xFFFF CPU internal RAM (128 bytes)\nFont data lives inside the BIOS at offset 0x200, accessed via\nget_font() for the VDP character rendering (src/vm/scv/vdp.cpp).\n'} cartridge_loading: - formats: cart, bin, rom, 0 (multi-file: .0/.1/.2/.3), zip - banking: 4 banks of 32 KB via PC5/PC6 port lines - source_ref: src/vm/scv/memory.h, src/vm/scv/memory.cpp

Technical notes

Libretro port of eSCV by Takeda Toshiya (Common Source Code Project), ported to libretro by MARCONATO Maxime. Upstream source mirrored at https://github.com/tautologico/common-src-project (src/vm/scv/).

BIOS loading in src/vm/scv/memory.cpp:initialize() (lines 74-243). Tries filenames in order: upd7801g.s01, upd7801g.bin, upd7801g.bios, bios.rom, bios.bin. First successful open wins. Upstream eSCV uses only BIOS.ROM (uppercase); the libretro port renamed and added fallback aliases.

The BIOS is read as 0x1000 (4096) bytes into the bios[] array, mapped read-only at CPU address 0x0000-0x0FFF (UPD7801 internal ROM area).

When CHECKBIOS core option is YES, the core computes MD5 of the loaded data and compares against 635a978fd40db9a18ee44eff449fc126. If the hash does not match, the BIOS is rejected (zeroed out, bios_present=false). When CHECKBIOS is AUTO (default) or NO, any file content is accepted. The log message for AUTO says "automatic (yes)" but the code skips the check (code bug: != YES_VAL at line 80).

The font/character data is embedded within the BIOS at offset 0x200 (memory.h get_font() returns bios + 0x200). No separate font ROM file.

The core can start without BIOS (supports_no_game=true) but shows "BIOS not found" or "Bad BIOS" on the OSD. Games will not run without it.

The .info declares firmware_count=1, firmware0_opt=false. Matches code.

1 files | 1 required, 0 optional | 1 in repo, 0 missing

`upd7801g.s01` -required

- System: scv
- Size: 4.0 KB
- MD5: `635a978fd40db9a18ee44eff449fc126`
- Aliases: `upd7801g.bin`, `upd7801g.bios`, `bios.rom`, `bios.bin`
- Validation: md5
- Source: `src/vm/scv/memory.cpp:74-243`
- Platforms: batocera, lakka, recalbox, retroarch, retrobat, retrodeck, retropie
- UPD7801G internal ROM (BIOS). Mapped at 0x0000-0x0FFF. Contains character font at offset 0x200.

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