melonDS: BIOS missing — set up NDS BIOS or use built-in HLE firmware

enable-hle-firmware-no-bios-files-needed (sortOrder=1, isMostHelpful)

Switch melonDS to HLE firmware mode — this uses the emulator's built-in DS firmware substitute and requires no BIOS files. Most commercial DS games run correctly under HLE and it is the fastest way to get started.

1. Open melonDS and go to Config → Emu settings (or File → Settings → DS-Mode). The exact menu path differs slightly between melonDS versions (0.9.x vs 1.x vs nightly builds), but look for a section called "BIOS/firmware" or "DS-Mode."
2. Enable "Use built-in HLE BIOS/firmware" (sometimes shown as "Use firmware built-in" or a checkbox labeled "Enable HLE firmware"). If this option is enabled, melonDS will not look for external BIOS files at all.
3. Leave the BIOS file paths blank or clear them if they currently point to non-existent files — a path to a missing file overrides the HLE setting in some versions.
4. Click OK / Apply and try launching a DS game. The DS boot animation will be skipped (HLE boots directly into the game) and most titles will run normally.
5. If a specific game crashes under HLE but you have confirmed others work, that game may require real BIOS accuracy. Note the title and follow S2 to set up real BIOS files for those edge cases.

Note: DSi-mode games and DSiWare always require real DSi BIOS + NAND files — HLE does not cover DSi mode. If your game is a DSi-enhanced or DSi-exclusive title, skip to S3.

dump-nds-bios-from-your-own-hardware (sortOrder=2)

Dump the BIOS and firmware from a Nintendo DS or DS Lite you own, then configure melonDS to use the real files. This gives the most accurate emulation and is required for a small number of games that fail under HLE.

1. What you need: a Nintendo DS, DS Lite, DSi, or 3DS family console that you own. Any of these can produce a valid NDS BIOS dump. You also need a way to run homebrew on that console (a flashcart for DS/DS Lite, or the homebrew launcher if your 3DS is CFW-enabled).
2. Use a BIOS dumping tool. The melonDS documentation and community (melonds.kuribo64.net) point to known tools for dumping the ARM7 BIOS, ARM9 BIOS, and firmware from NDS hardware. Search for "NDS BIOS dump homebrew" in the melonDS documentation. The tool will produce three files: bios7.bin, bios9.bin, and firmware.bin.
3. Verify the file sizes:
   • bios7.bin — exactly 16 384 bytes (16 KB)
   • bios9.bin — exactly 4 096 bytes (4 KB)
   • firmware.bin — 131 072 bytes (DS Lite) or 262 144 bytes (original DS / DSi). Both sizes are valid.
   If any file is the wrong size, the dump was incomplete — redo it.
4. Place the files in a dedicated folder on your PC (e.g. C:\Emulation\BIOS\NDS\).
5. In melonDS → Config → Emu settings → DS-Mode, disable HLE firmware and set each file path:
   • ARM7 BIOS → bios7.bin
   • ARM9 BIOS → bios9.bin
   • DS Firmware → firmware.bin
6. Click OK and launch a game. With real BIOS, melonDS will show the DS boot logo and health/safety screen before entering the game — this confirms real BIOS is active. The vast majority of DS games that had issues under HLE will now work correctly.

dsi-mode-requires-dsi-bios-and-nand (sortOrder=3)

DSiWare and DSi-exclusive titles require a separate set of DSi BIOS files plus a NAND image dumped from your own DSi or 3DS — regular NDS BIOS files are not enough for DSi-mode games.

1. What DSi mode needs (in addition to NDS BIOS):
   • dsibios7.bin — DSi ARM7 BIOS (65 536 bytes)
   • dsibios9.bin — DSi ARM9 BIOS (65 536 bytes)
   • dsifirmware.bin — DSi firmware (131 072 bytes)
   • dsinand.bin — a NAND image from your own DSi (size varies, typically 240–250 MB)
   All four must be dumped from a DSi or DSi-capable 3DS you own. None of these are derivable from a regular DS or DS Lite.
2. Dumping DSi BIOS: the melonDS documentation covers DSi BIOS dumping for 3DS consoles with CFW (via GodMode9 or a similar tool) and for DSi consoles directly. Follow the official melonDS wiki for the exact procedure — the steps differ between hardware types.
3. In melonDS → Config → Emu settings → DSi-Mode, supply the four DSi paths. Restart melonDS after saving.
4. To launch a DSi-mode game: right-click the ROM in melonDS and choose "Launch in DSi mode" (or enable DSi mode in settings). Games that are DS-only (not DSi-enhanced) do not benefit from DSi mode and should run under the standard DS profile from S1 or S2.
5. If you only own a DS or DS Lite (not a DSi or 3DS), you cannot dump DSi BIOS files legally. In that case, DSiWare and DSi-exclusive titles cannot be emulated with full accuracy — use the regular NDS HLE or BIOS path for standard DS games.