Changes

It's well-known enough that the Super Famicom was to get a CD add-on called the SNES-CD, developed by Sony who already helped with the sound chip for the SNES. However, Sony got greedy and tried to include a clause in the contract to give them all rights to any software developed on the device. In retaliation, Nintendo publicly humiliated the Sony executives present at the SNES-CD announcement by claiming they would partner with Phillips instead. Talks between Sony and Nintendo continued afterwards as late as 1993, but the project couldn't be salvaged. Nintendo lost interest in the CD peripheral, seeing how the Sega CD failed in the US and the PC-Engine CD only enjoyed modest success. They cancelled the Phillips collaboration on yet another SNES-CD prototype, but in return they allowed them to use some of their properties for their Phillips CD-i console. Later, they collaborated with the St. Giga radio service to create the Japan-exclusive Satellaview add-on for the Super Famicom which played broadcasts of SFC games using streamed audio. As for Sony, they took the hardware and experience from their collaboration with Nintendo to create the first PlayStation. Nintendo would continue to support the cartridge format for its next console, the Nintendo 64. A shy attempt at rewritable disk media was attempted with the 64DD, but the add-on failed due to the pathetic 64MB maximum storage limit which would be obsoleted by later bigger N64 cartridges, as well as the lack of support from third parties, many of whom had opted to support the PS1 instead. And the rest is history.

Some prototype units of the Sony SNES-CD were indeed made. While games were in development for the add-on, some were eventually reworked as regular SNES cartridge games with lots of content gutted (e.g. Nintendo R&D's Marvelous, Square's Secret of Mana and Romancing Saga 2). Other games, like Hook, were ported to other systems instead (Hook to the Sega CD instead, and Rayman to the Atari Jaguar, among others), while the rest were outright cancelled. These games were to have much bigger worlds, streamed music, cutscenes, and even FMVs according to various interviews. That never happened, however, and even most of the stuff developed for these consoles, including their various manuals and specifications, were lost.

 The only SNES-CD games available online at this time are a legitimate BIOS for one of the discovered prototypes and two homebrew games. These games, Magic Floor and Super Boss Gaiden (both of which have alternate versions as regular SNES ROMs) come as BIN/CUE files. NO$SNS 1.6 supports only one CD mode, so it doesn't actually read the CUE but just the BIN file. Both of these were tested on the real hardware and have severe visual glitches due to the SNES-CD adding more undocumented interrupts which are not accurately emulated anywhere, which means it's safe to say that while SNES-CD emulation exists nowadays, it would have low compatibility with any legit unreleased SNES-CD game prototypes.