<P> IBM's first hard drive, the IBM 350, used a stack of fifty 24 - inch platters and was of a size comparable to two large refrigerators . In 1962, IBM introduced its model 1311 disk, which used six 14 - inch (nominal size) platters in a removable pack and was roughly the size of a washing machine . This became a standard platter size and drive form - factor for many years, used also by other manufacturers . The IBM 2314 used platters of the same size in an eleven - high pack and introduced the "drive in a drawer" layout, although the "drawer" was not the complete drive . </P> <P> Later drives were designed to fit entirely into a chassis that would mount in a 19 - inch rack . Digital's RK05 and RL01 were early examples using single 14 - inch platters in removable packs, the entire drive fitting in a 10.5 - inch - high rack space (six rack units). In the mid-to - late 1980s the similarly sized Fujitsu Eagle, which used (coincidentally) 10.5 - inch platters, was a popular product . </P> <P> Such large platters were never used with microprocessor - based systems . With increasing sales of microcomputers having built in floppy - disk drives (FDDs), HDDs that would fit to the FDD mountings became desirable . Thus HDD Form factors, initially followed those of 8 - inch, 5.25 - inch, and 3.5 - inch floppy disk drives . Because there were no smaller floppy disk drives, smaller HDD form factors developed from product offerings or industry standards . </P> <Dl> <Dt> 8 - inch </Dt> <Dd> 6999241300000000000 ♠ 9.5 in × 6999117449599999999 ♠ 4.624 in × 6999361950000000000 ♠ 14.25 in (6999241300000000000 ♠ 241.3 mm × 6999117500000000000 ♠ 117.5 mm × 6999362000000000000 ♠ 362 mm). In 1979, Shugart Associates' SA1000 was the first form factor compatible HDD, having the same dimensions and a compatible interface to the 8" FDD . </Dd> <Dt> 5.25 - inch </Dt> <Dd> 5.75 in × 3.25 in × 8 in (146.1 mm × 82.55 mm × 203 mm). This smaller form factor, first used in an HDD by Seagate in 1980, was the same size as full - height 5 ⁄ - inch - diameter (130 mm) FDD, 3.25 - inches high . This is twice as high as "half height"; i.e., 1.63 in (41.4 mm). Most desktop models of drives for optical 120 mm disks (DVD, CD) use the half height 51⁄4" dimension, but it fell out of fashion for HDDs . The format was standardized as EIA - 741 and co-published as SFF - 8501 for disk drives, with other SFF - 85xx series standards covering related 5.25 inch devices (optical drives, etc .) The Quantum Bigfoot HDD was the last to use it in the late 1990s, with "low - profile" (≈ 25 mm) and "ultra-low - profile" (≈ 20 mm) high versions . </Dd> <Dt> 3.5 - inch </Dt> <Dd> 4 in × 1 in × 5.75 in (101.6 mm × 25.4 mm × 146 mm) = 376.77344 cm3 . This smaller form factor is similar to that used in an HDD by Rodime in 1983, which was the same size as the "half height" 31⁄2" FDD, i.e., 1.63 inches high . Today, the 1 - inch high ("slimline" or "low - profile") version of this form factor is the most popular form used in most desktops . The format was standardized in terms of dimensions and positions of mounting holes as EIA / ECA - 740, co-published as SFF - 8301 . </Dd> <Dt> 2.5 - inch </Dt> <Dd> 6998698500000000000 ♠ 2.75 in × 0.275--6998190499999999999 ♠ 0.75 in × 6999100202999999999 ♠ 3.945 in (6998698500000000000 ♠ 69.85 mm × 7--6998190000000000000 ♠ 19 mm × 6999100000000000000 ♠ 100 mm) = 48.895--6996132715000000000 ♠ 132.715 cm . This smaller form factor was introduced by PrairieTek in 1988; there is no corresponding FDD . The 2.5 - inch drive format is standardized in the EIA / ECA - 720 co-published as SFF - 8201; when used with specific connectors, more detailed specifications are SFF - 8212 for the 50 - pin (ATA laptop) connector, SFF - 8223 with the SATA, or SAS connector and SFF - 8222 with the SCA - 2 connector . </Dd> <Dd> It came to be widely used for HDDs in mobile devices (laptops, music players, etc .) and for solid - state drives (SSDs), by 2008 replacing some 3.5 inch enterprise - class drives . It is also used in the PlayStation 3 and Xbox 360 video game consoles . </Dd> <Dd> Drives 9.5 mm high became an unofficial standard for all except the largest - capacity laptop drives (usually having two platters inside); 12.5 mm - high drives, typically with three platters, are used for maximum capacity, but will not fit most laptop computers . Enterprise - class drives can have a height up to 15 mm . Seagate released a 7 mm drive aimed at entry level laptops and high end netbooks in December 2009 . Western Digital released on April 23, 2013 a hard drive 5 mm in height specifically aimed at Ultrabooks . </Dd> <Dt> 1.8 - inch </Dt> <Dd> 54 mm × 8 mm × 78.5 mm = 33.912 cm3 . This form factor, originally introduced by Integral Peripherals in 1993, evolved into the ATA - 7 LIF with dimensions as stated . For a time it was increasingly used in digital audio players and subnotebooks, but its popularity decreased to the point where this form factor is increasingly rare and only a small percentage of the overall market . There was an attempt to standardize this format as SFF - 8123, but it was cancelled in 2005 . SATA revision 2.6 standardized the internal Micro SATA connector and device dimensions . </Dd> <Dt> 1 - inch </Dt> <Dd> 42.8 mm × 5 mm × 36.4 mm . This form factor was introduced in 1999, as IBM's Microdrive to fit inside a CF Type II slot . Samsung calls the same form factor "1.3 inch" drive in its product literature . </Dd> <Dt> 0.85 - inch </Dt> <Dd> 24 mm × 5 mm × 32 mm . Toshiba announced this form factor in January 2004 for use in mobile phones and similar applications, including SD / MMC slot compatible HDDs optimized for video storage on 4G handsets . Toshiba manufactured a 4 GB (MK4001MTD) and an 8 GB (MK8003MTD) version and holds the Guinness World Record for the smallest HDD . </Dd> </Dl>

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