The “development” version of that is even crazier: it's a very tiny signed bootloader that does nothing but copies the “real” bootloader into memory, then trampolines into it, such that even developing your own IPL3 doesn't require having to re-brute-force the signature for every build.

And on top of that, libdragon's IPL3 doesn't just blindly copy the first megabyte of ROM code into RDRAM like the official Nintendo one does, but actually expects the ROM data after it to be a full-blown ELF executable, which it parses out and copies pieces of to the specified places.

Pretty slick stuff.