The 5.25-inch hard disk drive was introduced in 1980 by Shugart Technology (which very soon became Seagate Technology) in the form of the ST506 drive with a capacity of 5 MB.
The size of the drive followed that of the full-height 5.25-inch minifloppy disk drive (3.25-inches high), and meant the drive could fit into a floppy disk drive bay in a microcomputer. Half-height drive bays (1.625-inches high) became more commonplace through the 1980s, and half-height hard disk drives became available.
Hard disk drives were uncommon in microcomputers at the time, with most using floppy disks or cassettes for storage. The first IBM PC to come with a hard disk drive as standard was the PC XT of 1983.
Despite the widespread availability of smaller hard disk drives such as the 3.5-inch and 2.5-inch form factors, Quantum manufactured 5.25-inch hard disk drives under the Bigfoot name until the late 1990s, and Seagate sold the full-height Elite 47 drive (offering 47 GB) until around 2000. The larger platters had the advantage of lower data density and hence cost for the same capacity, and PCs of the time still contained 5.25-inch form factor drive bays since CD-ROM drives still used them.
