In more detail, 21fx is a new SNES hardware device. It gives the SNES the ability to stream up to 4GB of data, and to play back CD-quality 44.1KHz 16-bit stereo sound. These two combined allow the SNES to stream high-quality full-motion video. The above image is real, and it really does run 240x160 video at 20fps with 32KHz stereo audio. More @Wikipedia
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