libretro/wiki/troubleshooting.md

Troubleshooting

Game won't start / black screen

Most launch failures are caused by a missing or incorrect BIOS file.

Check what is in your BIOS folder

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --check

It hashes what is there and writes nothing. Anything counted as needing downloading is absent, and a required file that is absent means the core cannot start games for that system at all. --system narrows the check to one system (--list-systems names them):

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --check --system sony-playstation --verbose

Check if the hash matches

The count --check prints says how many files are present with contents the platform does not accept:

Checking existing files...
  1/109 present (0 verified, 1 wrong hash)

With --verbose the list under it names each one (wrong hash: scph5501.bin). The check hashes every file, on RetroArch too, where the frontend itself only looks for the name. Common causes:

• Wrong region (a PAL BIOS instead of NTSC, or vice versa)
• Wrong hardware revision (e.g. SCPH-5501 vs SCPH-1001 for PlayStation)
• Corrupted download

Running the same command without --check replaces each file with a wrong hash by a verified copy. Each system page on the site also lists the expected hashes, to compare against your file's MD5 or SHA1 by hand.

Wrong region BIOS

Some cores require region-specific BIOS files. A Japanese BIOS won't boot North American games on cores that enforce region matching. Check the emulator profile for your core to see which regions are supported and which files correspond to each.

BIOS not found by emulator

The file exists on disk, but the emulator reports it as missing.

Wrong directory

Each platform expects BIOS files in a specific base directory:

• RetroArch: system/ inside the RetroArch directory
• Lakka: /storage/system/
• Batocera: /userdata/bios/
• Recalbox: /recalbox/share/bios/
• RetroPie: ~/RetroPie/BIOS/
• ROCKNIX: /storage/roms/bios/
• MiSTer FPGA: /media/fat/games/
• BizHawk: Firmware/ inside the BizHawk directory
• EmuDeck: ~/Emulation/bios/
• RetroDECK: ~/retrodeck/bios/
• RetroBat: bios/ inside the RetroBat directory

Some cores expect files in subdirectories (e.g. dc/ for Dreamcast, pcsx2/bios/ for PlayStation 2). Check the path: field in the emulator profile for the exact expected location relative to the base directory.

Wrong filename

Cores match BIOS files by exact filename. If a core expects scph5501.bin and your file is named SCPH-5501.BIN, it won't be found on platforms that do exact name matching.

Check the emulator profile for the expected filename and any aliases listed under aliases:. Aliases are alternative names that the core also accepts.

Case sensitivity

Linux filesystems are case-sensitive. A file named Bios.ROM won't match a lookup for bios.rom. Windows and macOS are case-insensitive by default, so the same file works there but fails on Linux.

Batocera's verification uses casefold() for case-insensitive matching, but the actual emulator may still require exact case. When in doubt, use the exact filename from the emulator profile.

The RetroArch pack is built for every system RetroArch runs on, so it holds one name per file: BIOS.col, never bios.col beside it, since extracting both on Windows or macOS would overwrite one with the other. On Linux, Mesen-CE opens bios.col and NP2kai opens the lowercase np2kai/2608_*.wav, which the pack only holds as BIOS.col and 2608_*.WAV. The installer checks whether the BIOS directory keeps case and, if it does, also fetches these names. If you extract the ZIP on Linux by hand, take the Lakka pack instead: it is the RetroArch pack with both spellings. Releases up to v2026.10.10 have no Lakka pack of their own (RetroArch_Lakka_*_BIOS_Pack.zip serves both and holds one spelling), so with those use the installer.

The reverse happens on Batocera and Recalbox, whose lists hold both spellings because their systems keep case: NP2kai reads np2kai/bios.rom and np2kai/BIOS.ROM as two different files. Written to a folder that folds case (the share opened from Windows, an exFAT card), one overwrites the other. The installer checks the folder first, keeps one file per name there and lists the ones it left out.

Hash mismatch / UNTESTED

This section and the two after it are about this repository's own tools, run from a clone. scripts/verify.py checks the collection in bios/ against each platform, never your BIOS folder: for that, use --check above.

verify.py reports UNTESTED for a file of the collection that was hashed and does not match what the platform declares. The line gives the reason:

  UNTESTED (required): nintendo-ds/dsifirmware.bin: declared hash contradicted by the local file

The system page on the site lists every known version of the file with its expected MD5 and SHA1.

Existence-mode platforms never report UNTESTED

On RetroArch, Lakka and RetroPie, the platform check only asks whether the file is there, so the only outcomes are OK and MISSING. verify.py adds the emulator ground truth from the profiles and flags a DISCREPANCY when a file passes the platform check but fails the emulator's own size or hash validation.

The .variants/ directory

When multiple versions of the same BIOS exist (different revisions, regions, or dumps), the primary version lives in the main directory and alternatives live in .variants/. verify.py checks the primary file first, then falls back to variants when resolving by hash.

If your file matches a variant hash but not the primary, it's a valid BIOS -- just not the preferred version. Some cores accept multiple versions.

Pack is missing files

A generated pack doesn't contain all the files you expected.

Severity levels

verify.py assigns a severity to each issue, counted under severity_counts in its --json output. Not all missing files are equally important:

Severity	Meaning	Action needed
CRITICAL	Required file missing on an MD5 or SHA1 platform	Must fix. Core won't function.
WARNING	Optional file missing on an MD5 or SHA1 platform, hash mismatch (UNTESTED) on any hash platform, or a required file missing on an existence platform	Core works but with reduced functionality, or runs on content nobody verified.
INFO	Optional file missing on an existence-only platform, or a missing file the core covers with an HLE fallback	Core works fine, BIOS improves accuracy.
OK	File present and verified	No action needed.

The full mapping, including how hle_fallback overrides the platform mode, is in verification modes.

Focus on CRITICAL issues first. WARNING files improve the experience but aren't strictly necessary. INFO files are nice to have.

Large files (release assets)

Files like PS3UPDAT.PUP, PSVUPDAT.PUP, and Switch firmware are too large for the git repository. They are stored as GitHub release assets under the large-files release and downloaded at build time.

If a pack build fails to include these, check your network connection. In offline mode (--offline), large files are only included if already cached locally in .cache/large/.

Data directories

Some cores need entire directory trees rather than individual files (e.g. Dolphin's Sys/ directory, PPSSPP's assets/). These are fetched by refresh_data_dirs.py from upstream repositories.

In offline mode, data directories are only included if already cached in data/. Run python scripts/refresh_data_dirs.py to fetch them.

verify.py reports errors

How to read and interpret verify.py output.

Status codes

Status	Meaning
OK	File present, hash matches (or existence check passed)
UNTESTED	File present, hash not confirmed against the expected value
MISSING	File not found in the repository
DISCREPANCY	The platform check passes, an emulator's own check fails

Reading the output

The first line counts the platform's files and names its check. Under it come the entries that need attention, one per line as STATUS (required|optional): system/file, followed by a reason where there is one, then the counts of the files the emulator cores add. From python scripts/verify.py --platform retrodeck:

RetroDECK: 2007/2008 OK, 1 untested [md5]
  UNTESTED (required): nintendo-ds/dsifirmware.bin: declared hash contradicted by the local file
  DISCREPANCY: nintendo-snes/sgb2.boot.rom: RetroDECK says OK but supersnes9x says size mismatch: got 524288, accepted [256]
    supersnes9x [size]
  Core files: 1495 in pack, 0 required missing, 1 optional missing

--verbose also lists the passing entries that an emulator validates, with the check and the source lines behind it:

Recalbox: 351/351 OK [md5]
  OK (required): macintosh/MacII.ROM
    minivmac validates size=262144 [minivmac/cfg/CNFGRAPI.h:32, minivmac/src/OSGLUERETRO.c:781]

Cross-reference section

After per-file results, verify.py prints a cross-reference report. This lists files that emulator cores need but that the platform YAML doesn't declare. These files are still included in packs automatically, but the report helps identify gaps in platform coverage data.

The cross-reference uses resolve_platform_cores() to determine which emulator profiles are relevant for each platform, then checks whether each profile's files appear in the platform config.

Filtering output

# By platform
python scripts/verify.py --platform batocera

# By emulator core
python scripts/verify.py --emulator beetle_psx

# By system
python scripts/verify.py --system sony-playstation

# By hardware target
python scripts/verify.py --platform retroarch --target switch

# JSON for scripted processing: the entries that need attention
python scripts/verify.py --platform retroarch --json
# every entry, passing ones included, with its ground truth
python scripts/verify.py --platform retroarch --json --verbose

Installation script fails

Problems with install.py, install.sh, or download.sh.

Network issues

The installer fetches its manifest, then downloads only the repository or large-files release objects it needs. If a download fails:

• Check your internet connection
• Verify that https://github.com is reachable
• If behind a proxy, set HTTPS_PROXY in your environment
• Try again later if GitHub is experiencing issues

Permission denied

The installer needs write access to the target directory.

• On Linux/macOS: check directory ownership (ls -la) and run with appropriate permissions. Avoid running as root unless the target directory requires it.
• On Windows: run PowerShell as Administrator if installing to a protected directory.
• A file system mounted read-only refuses root too, so the installer does not suggest sudo for it. Linux remounts a card or drive read-only after an error (an unclean removal, for one): check it (fsck, or chkdsk on Windows) and mount it read-write again.

A file already in the BIOS folder with the read-only attribute is replaced like any other: on Windows the installer clears the attribute before putting the verified copy in place. file in place is read-only only appears when Windows refuses that too, which a file owned by another account can cause.

Platform not detected

The installer finds your platform from the config files it knows. If it finds none, name the platform and its BIOS folder.

Linux, macOS, Android (Termux):

curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --platform retroarch --dest ~/.config/retroarch/system
curl -fsSL https://raw.githubusercontent.com/Abdess/retrobios/main/install.sh | sh -s -- --platform batocera --dest /userdata/bios

Windows (PowerShell):

&([scriptblock]::Create((irm https://raw.githubusercontent.com/Abdess/retrobios/main/install.ps1))) `
  --platform retroarch --dest C:\RetroArch-Win64\system

--list-platforms lists the platforms the installer knows and the ones it finds here, and --help lists the options with examples.

Manifest or file not found

The one-line bootstrap verifies the downloaded installer before running it, and the installer reads its manifests from the same revision. A platform name is checked before anything is downloaded, so a "No file list" message comes from the revision: RETROBIOS_REF naming a tag that does not exist, or one older than the platform. Unset it, or pick a tag from the releases page. What a tag holds and for how long is under environment overrides.

Manual pack not found in release

If the installer reports that no pack exists for your platform, check available releases:

python scripts/download.py --list
# or
bash scripts/download.sh --list

A pack's name lists every platform it serves. Releases up to v2026.10.10 ship RetroArch and Lakka as one RetroArch_Lakka pack, and the next ones give Lakka its own, since Lakka runs on Linux where two names that differ by case are two files. The installer and the download scripts find the right pack either way.

A pack in several parts will not extract

Parts named Pack.part1of2.zip are ordinary ZIPs: extract each one into the same folder, and check that all of them were downloaded, the name says how many there are.

scripts/download.sh and scripts/download.py download every part and check it against the release's checksums before extracting. Both stage inside the destination directory, never in /tmp, which is a RAM disk on most of these systems.