The 1581 supports a rather simplistic imitation of directories which are really just partitions and largely unused. It implements faster burst mode access than the Commodore 1571 5¼" drive. The 1581 provides a total of 3160 blocks free when formatted (a block being equal to 256 bytes). It is the highest capacity serial bus drive ever made by Commodore, and the only 3½" one. However, Creative Micro Designs (CMD) made the FD2000 (1.6MB) and other 3½" disk drives. In July 2001, production and sale of the FD2000 was taken over by Click Here Software Co
See also: Commodore 64, Commodore 128, Commodore 1541, Commodore 1571