Anyone who has used the FDS remembers the iconic boot screen. A pixellated scrolls across a blue background reading "Please set disk card," followed by the trademark "© 1986 Nintendo." This is the user-facing element of the BIOS.
Whether you are trying to play the original Doki Doki Panic (which became Super Mario Bros. 2 ), the untranslated gem Ai Senshi Nicol , or the first Zelda with its original orchestral synth intro, remember: You cannot just download the game. You must also find the BIOS. -BIOS- NINTENDO FAMICOM DISK SYSTEM ROM
Expanded Audio: The BIOS manages the FDS’s extra wavetable synthesis channel, providing the rich, FM-like music that the standard NES lacked. Anyone who has used the FDS remembers the iconic boot screen