Hardware Reference
In-Depth Information
laptopand note topics stemshaveusedthem.Although21/2-inchdrivescanalsobeused
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:
• 8.5mm
• 9.5mm
• 12.5mm
• 12.7mm
• 17.0mm
• 19.0mm
The most popular sizes have been the 9.5mm and 12.5mm thick versions, with almost all
modern systems using the 9.5mm form factor. A thinner drive can almost always be in-
stalled 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.
The2.5-inchformfactorisalsocommonlyusedforSSDsandforhybriddrives(harddisk
drives that also include flash memory). To learn more about SSDs, see “
SSD (Solid-State
1.8-inch Drive
The 1.8-inch drive was introduced by Integral Peripherals in 1991 and has had problems
gainingacceptanceinthemarketplaceeversince.Thissizewasinitiallycreatedbecauseit
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 In-
tegral Peripherals' 1.8-inch drive technology for $5.5 million; 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. Of those, only Toshiba and Hit-
achi continue to manufacture drives in that format. HP exited the disk drive market com-
pletely in 1996, and Calluna finally ceased operation in 2001. Toshiba introduced its
1.8-inch drives (available in the physical format of a Type II PC Card) in 2000, and Hit-
achi entered the 1.8-inch drive market in 2003. The 1.8-inch drives are available in capa-
cities of up to 250GB from Toshiba; Hitachi drives have capacities ranging from 20GB to
80GB.
