Macintosh 800K External Drive

Apple introduced the 800K External Drive about the same time as the Macintosh Plus in 1986. The drive can use 800K DSDD (Double-Sided/Double Density) or 400K SSDD (Single-Sided/Double Density), but it was designed explicitly to take advantage of the higher capacity 800K disks compatible with the Plus and 512Ke. The drive can be used with any Macintosh that doesn't have an FDHD controller, which includes the Macintosh Plus, Macintosh SE, and Macintosh 512Ke. The drive will work with a Macintosh 512K, but in order to use it, you have to use the drive as a second drive with the HD20 INIT installed on the internal 400K boot floppy. This drive cannot be used with the original Macintosh because it lacks enough memory to support it. The 800K External Drive is not intended to be used with Apple II computers.