emulator: JAXE
type: libretro
core_classification: official_port
source: "https://github.com/kurtjd/jaxe"
upstream: "https://github.com/kurtjd/jaxe"
profiled_date: "2026-03-24"
core_version: "GIT"
display_name: "CHIP-8/S-CHIP/XO-CHIP (JAXE)"
cores:
  - jaxe
systems:
  - chip8

notes: |
  JAXE is a CHIP-8, SCHIP, and XO-CHIP emulator by Kurtis Dinelle,
  ported to libretro. Supports .ch8, .sc8, .xo8, and .hc8 ROMs.

  No external BIOS or font files required. The core has firmware_count = 0
  in jaxe_libretro.info and never calls RETRO_ENVIRONMENT_GET_SYSTEM_DIR.

  Font data is hardcoded in chip8_load_font() at src/chip8.c:118-168.
  The standard 4x5 hex font (0-F, 80 bytes) is loaded at address 0x000,
  and the SCHIP 8x10 big hex font (0-F, 160 bytes) follows immediately
  after at address 0x050. Both are written directly into chip8->RAM[]
  during chip8_reset() -> chip8_load_font().

  Memory layout from include/chip8.h:42-45:
    0x000-0x04F  standard font (NUM_FONT_BYTES = 80)
    0x050-0x0EF  big font (NUM_BIG_FONT_BYTES = 160)
    0x0F0-0x0FF  stack (STACK_SIZE = 16)
    0x100-0x10F  audio buffer (AUDIO_BUF_SIZE = 16)
    0x200+       program ROM (PC_START_ADDR_DEFAULT)

  The fonts/dbgfont.ttf file in the repo is only used by the standalone
  build (src/main.c:19) for the SDL debugger overlay, not by the
  libretro core.

files: []

platform_details:
  bios_mapping:
    target: "none"
    source_ref: "jaxe_libretro.info:17, src/chip8.c:118-168"
    note: |
      All font/sprite data is compiled into the binary. The standard
      CHIP-8 hex font (5 bytes per character, 16 characters) and the
      SCHIP big hex font (10 bytes per character, 16 characters) are
      stored as a static array in chip8_load_font() and copied into
      RAM on every reset. No file I/O is performed for BIOS or fonts.