Hardware Reference
In-Depth Information
Currently, 3 1/2-inch drives are the most popular for desktops, whereas 2 1/2-inch and smaller drives
are popular in laptops and other portable devices. Parallel ATA (PATA) drives have been replaced
by SATA drives in new systems. PATA drives will still be available for upgrading older systems,
although the choices are becoming more limited.
5 1/4-Inch Drive
Shugart Associates introduced the 5 1/4-inch form factor along with the first 5 1/4-inch floppy drive
in 1976. The story goes that founder Al Shugart then left that company and founded Seagate
Technologies, which introduced the first 5 1/4-inch (Model ST-506, 5MB capacity) hard disk in
1980, predating the IBM PC. IBM later used the Seagate ST-412 (10MB) drive in some of its PC-XT
models, which were among the first PCs to be sold with hard drives built in. The physical format of
the 5 1/4-inch hard disk back then was the same as the 5 1/4-inch full-height floppy drive, so both fit
the same size bay in a chassis. For example, the original IBM PC and XT models had two 5 1/4-inch
full-height bays that could accept these drives. The first portable systems (such as the original
Compaq Portable) used these drives as well. Later, the 5 1/4-inch form factor was reduced in height
by one-half when the appropriately named 5 1/4-inch half-height floppy drives and hard drives were
introduced. This allowed two drives to fit in a bay originally designed for one. The 5 1/4-inch half-
height form factor is still used as the form factor for optical drives and is the standard form factor for
larger drive bays in all modern desktop PC chassis.
3 1/2-Inch Drive
Sony introduced the first 3 1/2-inch floppy drive in 1981, which used a smaller width and depth but
