Hardware Reference
In-Depth Information
the same height as the half-height 5 1/4-inch form factor. These were called
3 1/2-inch half-height
drives
, even though there was no such thing as a “full-height” 3 1/2-inch drive. Rodime followed with
the first 3 1/2-inch half-height hard disk in 1983. Later 3 1/2-inch floppy and hard drives would be
reduced in height to only 1 inch, which was just under one-third of the original 5 1/4-inch full-height
form factor. (These were sometimes called
1/3-height drives
.) Today, the 1-inch high version has
become the modern industry-standard 3 1/2-inch form factor.
2 1/2-Inch Drive
PrairieTek introduced the 2 1/2-inch form factor in 1988, which proved to be ideal for laptop and
notebook computers. As laptop sales grew, so did sales of the 2 1/2-inch drives. Although PrairieTek
was the first with that form factor, other drive manufacturers quickly capitalized on the market by also
introducing 2 1/2-inch drives. Finally, in 1994 Conner Peripherals, Inc., paid $18 million for
PrairieTek's 2 1/2-inch disk drive technology, and PrairieTek went out of business. Since the 2 1/2-
inch drives first appeared, virtually all laptop and notebook systems have used them. Although 2 1/2-
inch drives can also be used in desktop systems, the 3 1/2-inch drive continues to dominate the
desktop market due to greater capacity and speed and lower cost.
The 2 1/2-inch drives have been manufactured in various thicknesses (or heights), and many notebook
and laptop systems are restricted as to how thick a drive they can support. Here are the common
thicknesses that have been available:
• 7mm
• 8.5mm
• 9.5mm
• 12.5mm
• 12.7mm
• 17.0mm
• 19.0mm
The most popular sizes over the years have been the 9.5mm and 12.5mm thick versions; however,
most current systems use the 9.5mm or 7mm form factors. A thinner drive can almost always be
installed in place of a thicker one; however, most systems do not have the room to accept a thicker
drive than they were originally designed to use.
The 2.5-inch form factor is also commonly used for SSDs and for hybrid drives (hard disk drives that
also include flash memory).
Storage
.”
1.8-Inch Drive
The 1.8-inch drive was introduced by Integral Peripherals in 1991 and has had problems gaining
acceptance in the marketplace ever since. This size was initially created because it fit perfectly in the
PC Card (PCMCIA) form factor, making it ideal as add-on removable storage for laptop and
notebook systems. Unfortunately, the 1.8-inch drive market was slow to take shape, and in 1998 an
investment group called Mobile Storage bought Integral Peripherals' 1.8-inch drive technology and
Integral Peripherals then went out of business. Several other companies have introduced 1.8-inch
drives over the years—most notably HP, Calluna, Toshiba, and Hitachi. HP exited the disk drive
