BIOS Files Explained: Which Emulators Need Them & Where to Put Them
One of the most confusing parts of emulation is BIOS files. Some consoles need them, some don't, and putting them in the wrong folder means your game simply won't boot. Here's a clear, practical guide.
What is a BIOS file?
A BIOS (Basic Input/Output System) is a small piece of firmware that the original console used to start up. Some emulators need an exact copy of this firmware to run games correctly. Others have built-in replacements (HLE — High-Level Emulation) that skip the BIOS entirely.
Think of it like this: the BIOS is the console's "boot screen." Some emulators simulate that boot screen in software. Others need the real thing.
Which consoles need BIOS files?
Always required:
- PS1 — scph5501.bin (or scph1001.bin, scph5500.bin depending on region)
- PS2 — Multiple BIOS files (SCPH-70012 recommended for NTSC-U)
- Sega Saturn — saturn_bios.bin
- Sega CD — bios_CD_U.bin / bios_CD_E.bin / bios_CD_J.bin
- Neo Geo — neogeo.zip (MAME format)
Optional but recommended:
- GBA — gba_bios.bin (most cores work without it, but some games have intro glitches)
- DS — bios7.bin, bios9.bin, firmware.bin (MelonDS works without for most games)
- Dreamcast — dc_boot.bin, dc_flash.bin (Flycast can run many games without them)
Not needed:
- NES — No BIOS required
- SNES — No BIOS required
- N64 — No BIOS required
- Game Boy / Game Boy Color — No BIOS required (optional for boot logo)
- Mega Drive / Genesis — No BIOS required
Where to put BIOS files
The standard location is a "system" folder. The exact path depends on your setup:
RetroArch: Place BIOS files in the "system/" folder inside your RetroArch directory. You can check or change this path in Settings → Directory → System/BIOS.
RetroApp: Drop BIOS files into any of these locations: - "AppData/Roaming/RetroApp/system/" - Your RetroArch "system/" folder (RetroApp checks both automatically)
RetroApp will tell you exactly which BIOS files are missing when you try to launch a game that needs them. No guessing.
Common BIOS problems
Game boots to a black screen — 99% of the time, a missing or wrong BIOS file. Check the emulator log for the exact filename it's looking for.
Wrong region BIOS — A Japanese PS1 BIOS won't boot American games. Match the BIOS region to your ROM region, or use a multi-region BIOS like scph5501.bin which handles most cases.
File is the wrong size — BIOS files have exact sizes. A PS1 BIOS is always 512 KB. If yours is larger or smaller, it's likely corrupted or the wrong file.
Filename mismatch — Emulators expect exact filenames, usually lowercase. Rename your files to match exactly what the core expects (e.g., scph5501.bin, not SCPH5501.BIN).
RetroApp's BIOS checker
RetroApp includes a built-in BIOS checker that scans your system folders at startup. If a BIOS file is missing, you'll see a clear warning with: - The exact filename needed - The folder where it should go - Which consoles are affected
No more forum threads, no more trial and error.