Nintendo 64DD

The 64DD is the magnetic disk drive that only ever shipped in Japan, and the reason there is a hatch in the Nintendo 64’s floor. It is taller than the console it carries: the N64 stands on top of it, and a cartridge can be in the console while a disk is in the drive.

Put your disks in roms/nintendo_64dd. See expansion hardware for how to stack the two.

Two cores, two halves of the library

Neither N64 core can do all of the 64DD, so which one runs depends on what you are playing. RetroXR picks for you; this is what it is picking between.

What you are playing	Core
Disk only — Mario Artist, Kyojin no Doshin	parallel_n64
Cartridge + expansion disk — F-Zero X Expansion Kit	mupen64plus_next

mupen64plus_next refuses a bare .ndd outright — it does not list the extension at all, so you get “failed to load ROM” and nothing rendered. parallel_n64, in turn, cannot do the cartridge-plus-disk pairing. Hence both.

Playing a cartridge with its expansion disk

Put the ordinary cartridge into the console’s own slot, on top of the stack, and the expansion disk into the drive underneath. That is the whole of it.

RetroXR hands the core both at once, through mupen64plus_next’s ndd subsystem, in the order the core asks for them: disk first, cartridge second, which is the reverse of which one a lone machine would boot from.

So for the worked example: the Japanese F-Zero X cartridge goes in the console, and the F-Zero X Expansion Kit disk goes in the drive.

Any of the usual dump formats work

The disk format is detected from the file’s content and size rather than from its extension, so MAME and D64 dumps load just as well as anything else.

The IPL is mandatory

The 64DD has its own boot ROM, and you have to supply it: the Japanese retail IPL, 4 MiB, md5 8d3d9f294b6e174bc7b1d2fd1c727530. Where it goes depends on which core is running, so install both:

Core	Path
parallel_n64	system/parallel_n64/64DD_IPL.bin
mupen64plus_next	system/mupen64plus_next/Mupen64plus/IPL.n64

Both cores declare it optional. It is not.

The .info files mark the IPL optional, and that flag is simply wrong here — believe the measurement, not the declaration.

Without it, parallel_n64 logs “Disabling 64DD” and then the process dies: exit 127, with no crash handler, which looks like a hang rather than a fault. If a 64DD launch appears to freeze RetroXR, the missing IPL is the first thing to check.

Telling whether the disk actually attached

Nothing is printed either way, so the game’s own screen is the only oracle — and a cartridge that merely booted looks exactly like a success until you read it.

The worked example is F-Zero X. On its own, the title screen reads (c) 1998 Nintendo. With the Expansion Kit attached, the same screen gains a 64DD line and reads (c) 1998, 1999. Run the cartridge alone once so you know what the negative looks like.

Where disk saves go

The two cores disagree, and it is worth knowing which one you are on.

mupen64plus_next writes beside the disk, as <diskname>.disk_save, and repoints writes at that file so your original dump is never modified. The consequence to design around: if your ROM folder is read-only, 64DD saves fail silently with only a warning.

parallel_n64 instead writes a 62 MB save per disk into its own system folder.