BIOS Management

Some emulated systems require BIOS files to run games. Without the correct BIOS files, games for those systems will fail to launch. The plugin can download BIOS files directly from your RomM server.

What Are BIOS Files?

BIOS (Basic Input/Output System) files are firmware dumps from original hardware. Emulators need them to accurately simulate the console's boot process. Common examples:

• PlayStation — scph5501.bin (and other regional variants)
• Dreamcast — dc_boot.bin, dc_flash.bin
• Saturn — sega_101.bin, mpr-17933.bin

Not all systems need BIOS files. Cartridge-based systems like Game Boy, SNES, and Genesis typically work without them.

BIOS Status on the Game Detail Page

When you open a game that belongs to a platform with BIOS files on your RomM server, the game detail panel shows a BIOS status indicator:

• Green — "BIOS ready (X files)" — all BIOS files are downloaded
• Orange — "BIOS required — X/Y downloaded" — some files are missing

Tap the BIOS status indicator to see a detailed list of individual files and which ones are present or missing.

BIOS Manager

The dedicated BIOS management page shows all platforms that have firmware files on your RomM server.

1. From the main QAM page, tap BIOS Files
2. Platforms with synced games that need BIOS files appear first, marked with "BIOS needed"
3. Each platform shows how many files are downloaded vs. available (e.g. "3 / 5 files")
4. Tap Show Files to see the individual file list for a platform
5. Tap Download All to download all missing BIOS files for a platform

BIOS files are downloaded to your RetroDECK bios directory (e.g. ~/retrodeck/bios/). Some platforms use subdirectories — for example, Dreamcast BIOS goes into bios/dc/ and PS2 BIOS goes into bios/pcsx2/bios/. The plugin handles the correct placement automatically.

Which Systems Need BIOS?

This depends on what's uploaded to your RomM server. Common systems that require BIOS files include PlayStation, PS2, Saturn, Dreamcast, and some arcade systems. The plugin only shows BIOS status for platforms that have firmware files in your RomM library.

Per-Platform BIOS Filtering

The plugin only shows BIOS files that belong to the platform you're looking at. For example, a GBA game page shows gba_bios.bin only — not Game Boy or Game Boy Color BIOS files, even though the emulator core (mGBA) supports all three systems. This filtering is built into the BIOS registry and works automatically.

Active Core Detection

Different emulator cores can have different BIOS requirements for the same platform. The plugin detects which core RetroDECK is actually configured to use and filters the BIOS list accordingly, so you only see the files that matter for your setup.

Example: Game Boy Advance

• With mGBA (RetroDECK's default), gba_bios.bin is shown as optional — mGBA has a built-in high-level BIOS replacement
• With gpSP, gba_bios.bin is shown as required — gpSP cannot run without it

The active core name appears as a badge in both the game detail page BIOS indicator and the BIOS Manager. This tells you at a glance which core the plugin is filtering for.

How the core is determined:

1. If a per-game override exists in ES-DE's gamelist.xml (via <altemulator>), the plugin uses that first
2. If no per-game override, the plugin checks for a per-system override in gamelist.xml (via <alternativeEmulator>)
3. The plugin reads RetroDECK's ES-DE configuration (es_systems.xml) from the flatpak installation to find the default emulator for each platform — the first listed RetroArch core is treated as the default
4. If the live configuration can't be read, the plugin falls back to a shipped core_defaults.json with RetroDECK's known defaults
5. If all detection fails, all BIOS files for the platform are shown — the safe default

The detection chain ensures BIOS filtering works even when RetroDECK's configuration files aren't accessible (e.g. after an update changes paths). You'll see a "Core: mGBA" badge when detection is working, or no badge when falling back to showing all files.

Changing the Active Core

You can change the active emulator core directly from the plugin, without leaving Game Mode. Changes are written to ES-DE's gamelist.xml so they persist across sessions and are picked up by both the plugin and ES-DE.

Per-Platform (BIOS Manager)

In the BIOS Manager, platforms with multiple available cores show an Active Core dropdown. Changing this sets the default core for all games on that platform.

1. Open the BIOS Manager from the main QAM page
2. Find the platform you want to change
3. Use the Active Core dropdown to select a different core
4. The BIOS file list updates immediately to show files relevant to the new core

This writes a system-wide override to ES-DE's gamelist.xml. ES-DE will pick up the change on next launch. The BIOS Manager works even when your RomM server is offline — core switching and BIOS status are available, only download buttons are disabled.

Per-Game (Game Detail Page)

On the game detail page, a CPU button (microchip icon) appears between the RomM and Steam gear buttons when multiple cores are available for the game's platform.

1. Open a game's detail page
2. Tap the CPU button (microchip icon)
3. Pick a core from the menu — the current core is marked with a checkmark
4. The BIOS status, core badge, and game info panel update immediately

A per-game override takes priority over the platform default. To reset back to the platform default, select the default core (marked with "(default)") from the menu — this clears the per-game override.

Non-Default Core Indicator

The CPU button changes color to indicate the active core status:

• Gray — the default core is active (no overrides)
• Yellow — a non-default core is active (per-game or per-platform override)

The game detail info panel shows the active core in a dedicated "Emulator" column alongside the BIOS status, using a two-column layout.

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