The Atari 810 Disk Drive was Atari's first disk drive for its line of Atari 400/800 computers.   Providing 88K of storage per disk side, the 810 gave Atari computer users the ability to quickly store and retrieve documents and program files to and from the storage device.   Up to 4 Atari 810's could be daisy chained together via the Atari SIO bus for a total of almost 360K of on-line random access file storage and retrieval.   The Atari 810 came in two different versions; the Tandon mech version and the MPI mech version.    The Atari 810 is rather large compared to other companies disk drives and has an external 9Vac power supply.   The reason why the drive is so large is that there is no disk drive controller in any of the Atari 400/800 computers, instead each device that connects to an Atari computer through its SIO bus is actually an intelligent device with its own intelligent communications controller and floppy disk controller.