The 64DD (for Dynamic Drive) was a floppy disc peripheral for the Nintendo 64, and was introduced by Nintendo in 1999.
It was intended to be Nintendo’s answer to the cheaper-to-produce CD-ROM that was used for the rival Sony PlayStation. The discs for the 64DD were rewritable and had a storage capacity of 64 MB. The games on normal Nintendo 64 ROM cartridges could also hook up with 64DD expansions, for extra levels, minigames, or saving personal data. The 64DD came with a modem that allowed users to connect to Randnet, an online service for Nintendo 64 users.
It was a commercial failure, and only ten titles were released for it. It was never released outside Japan, and was discontinued in 2000.