Originally planned for a 1994 release, the SNES CD-ROM started its life as a partnership project with Sony. However, due to licencing disagreements, Nintendo dropped the partnership and turned to Sony’s rival, Phillips. Alas, unfortunately for Nintendo, the only thing that came of it was Sony’s eventual entrance into the console market.
Lucky for us, however, documentation has surfaced for this long cancelled add-on. Click the link below to view the PDF.
PDF Documentation: SNES CD-ROM System – 1993