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RetroBIOS

FreeChaF

FreeChaF emulates Fairchild Channel F. It reads 3 files, none of them required: it starts games without them.

About this profile
Detail Value
Type libretro
Classification Pure libretro
Source https://github.com/libretro/FreeChaF
Version 1.0, stated in src/libretro.c
Revision libretro/FreeChaF@76c7a84f1f7e
Profiled 2026-03-23
Profile YAML, JSON
Cores freechaf
Systems Fairchild Channel F
Install this emulator's files

The installer finds your setup and its BIOS folder, then downloads only the files this emulator reads there and checks each one.

Open the Start menu. Type PowerShell and open it. Paste the line. Press Enter.

PowerShell
&([scriptblock]::Create((irm https://abdess.github.io/retrobios/i.ps1))) --emulator freechaf
Platform details

  • bios_mapping:

    • target: 0x000-0x7FF in 64K memory space
    • source_ref: src/memory.h:27-29, src/memory.c:29-61
    • note: MEMORY_loadSysROM_libretro() reads the file and copies it into Memory[] at the given address offset. PSU1 is loaded at 0x000, PSU2 at 0x400. The loader caps file size to (MEMORY_SIZE - address) to prevent overflow. MEMORY_RAMStart is advanced past the loaded ROM to protect it from writes.

  • hle_fallback:

    • source_ref: src/channelf_hle.c
    • note: When BIOS files are missing, FreeChaF uses HLE to emulate the PSU routines in software. This is marked as experimental and may cause compatibility issues with some games. Each PSU can independently fall back to HLE.

  • load_priority:

    • source_ref: src/libretro.c:186-198
    • note: PSU1 loading order: sl90025.bin (Channel F II) first, then sl31253.bin (original Channel F) as fallback. If both fail, HLE is used. sl90025.bin is the preferred BIOS as it includes Channel F II improvements.
Technical notes

FreeChaF is a Fairchild Channel F emulator written for libretro.

BIOS loading is in src/libretro.c:186-208. The core first tries to load sl90025.bin (Channel F II PSU1) at address 0x000. If that fails, it falls back to sl31253.bin (original Channel F PSU1) at the same address. PSU2 (sl31254.bin) is always loaded at address 0x400.

Memory layout from src/memory.h:27-30: 0x000-0x3FF PSU1 ROM (sl31253 or sl90025) 0x400-0x7FF PSU2 ROM (sl31254) 0x800-0x1FFF cartridge ROM 0x2000+ VRAM

If either PSU ROM fails to load, the core switches to experimental HLE (high-level emulation) for that PSU. A warning message is shown to the user recommending real BIOS files. HLE state is tracked per-PSU via hle_state.psu1_hle and hle_state.psu2_hle (src/channelf_hle.c).

The .info file declares all three firmware files as required (opt=false), but the core does not abort on missing BIOS -- it falls back to HLE.

Files

Section titled “Files”

3 files: 0 required, 3 optional. 3 have an HLE fallback.

In this collection: 3 in repo and 0 missing.

Optional

Section titled “Optional”

sl31253.bin optional in repo HLE fallback

  • System: Fairchild Channel F
  • Channel F PSU1 ROM (original). Fallback if sl90025.bin is missing.
Priority and source

sl31254.bin optional in repo HLE fallback

Source

sl90025.bin optional in repo HLE fallback

Priority and source

Next steps

Section titled “Next steps”
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Maintained by Abdess on GitHub. Report a problem.

Packs from release v2026.10.10, .

MIT for the tooling and metadata. BIOS and firmware files are third-party system software, preserved for personal backup, archival and interoperability.