I think you might be thinking of the Swyft Card, which was an Apple ][ card that implemented a number of similar features before the Cat was released. My Cat h

I think you might be thinking of the Swyft Card, which was an Apple ][ card that implemented a number of similar features before the Cat was released. My Cat has 256k of RAM and uses 800k floppies. However, by default it just copies the RAM straight to disk and doesn't use any more than 256k of the floppy. You CAN access the rest of the disk via FORTH, but it's a PitA and you don't really get a file system as much as a block device.