Skip to content

BBKEmu - RetroBIOS
Type standalone + libretro
Classification Pure libretro
Source https://github.com/AloysHF/BBKEmu
Version 0.1.0
Profiled 2026-09-03
Cores bbkemu
Systems bbk-longman-4980, bbk-longman-4988
Platform details

memory_map: - source_ref: crates/bbkemu-core/src/memory.rs:377-398 - note: Physical space seen through sixteen 4 KiB bank registers: RAM below

0x8000, 2 MiB flash at 0x200000, 8.BIN at 0x800000, E.BIN at 0xE00000. Reads outside a loaded image return 0x00; ROM windows ignore writes.

Technical notes

BBK A-series electronic dictionary game emulator written in Rust by AloysHF. The libretro core and the bbk-emu standalone binary share the bbkemu-core crate. A .gam game is 6502 code that calls into the dictionary's OS ROM for LCD, keyboard, audio, timer and file services.

Two ROM images are read from the system directory, in one subdirectory per model: {system}/BBKEmu//8.BIN, the font ROM mapped at physical 0x800000-0x9FFFFF, and E.BIN, the OS ROM mapped at 0xE00000-0xFFFFFF (crates/bbkemu-libretro/src/lib.rs:187-206, crates/bbkemu-core/src/memory.rs:377-398). The libretro core always loads content as the A4980 model (crates/bbkemu-libretro/src/lib.rs:470-471), so only BBKEmu/A4980/ is ever read from RetroArch. Both reads are std::fs::read guarded by if let Ok: a missing file is skipped without any message to the frontend. The image is copied into a 2 MiB zero-filled buffer (crates/bbkemu-core/src/memory.rs:197-209); nothing checks its size or contents.

Without E.BIN, run_os_init (crates/bbkemu-core/src/emulator.rs:231-252) sets PC to 0x350, reads zeros from the ROM window, never sees _MTCT=0xFE and gives up after 10 million cycles; the bank registers stay unmapped and the game exits at its first OS call. Measured by running run_os_init from bbkemu-core against a dump: 1 092 023 cycles to completion with E.BIN, timeout without it. Without 8.BIN the font window reads as 0x00 and every glyph the OS draws is blank; execution continues.

The standalone binary takes -8/--rom8 and -e/--rome explicit paths and otherwise reads system/BBKEmu//8.BIN and E.BIN relative to the working directory, --model 4980 (default) or 4988 selecting the subdirectory (crates/bbkemu/src/main.rs:108-117, crates/bbkemu/src/main.rs:146-170). The A4988 model differs by its flash save-area offset and key layout (crates/bbkemu-core/src/emulator.rs:148-153, crates/bbkemu-libretro/src/lib.rs:619-628).

During init the OS maps its own bank at logical bank D: 0xEA8 for the A4980 OS, 0xE88 for the A4988 OS (crates/bbkemu-core/src/model.rs:11-13). The core never reads that value back; detect_model (crates/bbkemu-core/src/model.rs:37-49) has no caller. The include_bytes! font in crates/bbkemu-core/src/font.rs is not declared in lib.rs and is not compiled. Content arrives through the frontend buffer (need_fullpath = false, crates/bbkemu-libretro/src/lib.rs:416). Save RAM is the first 0x14000 bytes of the emulated flash (crates/bbkemu-libretro/src/lib.rs:840-842).

4 files | 4 required, 0 optional | 4 in repo, 0 missing

8.BIN required in repo
BBK A-series font ROM

E.BIN required in repo
BBK A-series OS ROM

8.BIN required in repo standalone
BBK A-series font ROM, A4988 slot

E.BIN required in repo standalone
BBK A-series OS ROM, A4988 slot

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