"The Family Computer Disk System (ファミリーコンピュータ ディスクシステム, Famirī onpyūta Disuku Shisutemu, officially abbreviated as FDS)was released on February 21, 1986 by Nintendo as a peripheral for the Family Computer ("Famicom") console in Japan. It was a unit that used proprietary floppy disks for data storage. It was announced, but never released, for the North American Nintendo Entertainment System.
Through its entire production span, 1986-2003, 4.5 million units were sold. The device was connected to the Famicom deck by plugging a modified cartridge known as the RAM Adapter into the system's cartridge port, which attached via a supplied cable to the disk drive. The RAM adapter contained 32 kilobytes of RAM for temporary program storage, 8 kilobytes of RAM for tile and sprite data storage, and an ASIC known as the 2C33. The ASIC acted as a disk controller for the floppy drive, and also included additional sound hardware featuring primitive FM synthesis capabilities.
The floppy disks used were double-sided, with a capacity of 64 kilobytes per side. Many games spanned both sides of a disk, requiring the user to switch sides at some point during gameplay. A few games used two full disks (four sides). The Famicom Disk System was capable of running on six C-cell batteries or the supplied AC adapter. The battery option was included due to the likelihood of a standard set of AC plugs already being occupied by a Famicom and a television." (Wikipedia)
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