emux (CHIP-8) - RetroBIOS

Type	libretro
Classification	official_port
Source	https://github.com/libretro/emux
Upstream	https://github.com/sronsse/emux
Version	0.1
Profiled	2026-03-23
Cores	emux_chip8
Systems	chip8

Platform details

bios_mapping: - target: none - source_ref: mach/chip8.c:40-57, mach/chip8.c:98-115 - notes: No external BIOS. The 80-byte character font is compiled into the

binary as char_mem[] and memcpy'd into RAM[0x000] on every reset. This is standard CHIP-8 behavior -- all interpreters embed the font.

Technical notes

emux is a multi-system emulator supporting CHIP-8, Game Boy, NES, and Sega Master System as separate libretro cores. The CHIP-8 core (emux_chip8) does not require any external BIOS or firmware files.

The CHIP-8 architecture has no real BIOS. The standard font/character set (hex digits 0-F, 5 bytes each = 80 bytes) is hardcoded in mach/chip8.c:40-57 as the char_mem[] array. On reset, this font data is copied into the beginning of the 4 KB RAM (address 0x000-0x04F) via memcpy in chip8_reset() at mach/chip8.c:105.

ROM loading: the game ROM is loaded via file_open(PATH_DATA, ...) in chip8_init() at mach/chip8.c:68-74. On reset, ROM contents are copied into RAM starting at address 0x200 (mach/chip8.c:113). The core accepts .ch8, .bin, and .rom extensions (libretro/Makefile.rules:20).

Memory map from mach/chip8.c:17-20: 0x000-0x04F font/character data (hardcoded) 0x050-0x1FF unused 0x200-0xFFF program ROM + working RAM

The libretro frontend retrieves the system directory via RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY (libretro/libretro.c:34) but only uses it as a general config path, not for BIOS loading.

No BIOS or firmware files required.

Why no files

CHIP-8 has no BIOS, font data hardcoded in char_mem[]

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