Hardware Reference
In-Depth Information
fastest drives today.
• Average seek times (how long it takes to move the heads to a particular cylinder) have
decreased from more than 85ms (milliseconds) for the 10MB drives IBM used in the 1983
vintage PC-XT to as low as 3.3ms for 15,000 rpm drives today.
• My first 10MB hard drive/controller cost $1,695 for the drive and $695 for the controller in
1983. That's equal to more than $5,514 today! Currently you can get 2TB drives (with
integrated controller) for around $100 (or less), which means that the price of a typical hard
drive today costs well over 200 times less than what it did nearly 30 years ago. HDDs used to
be an expensive high-end component; now they are a cheap, almost disposable commodity.
Note
IBM left the hard disk business when it sold its Hard Disk Drive operations division to Hitachi
on January 6, 2003. Hitachi Global Storage Technologies (
www.hgst.com
), which was formed
to manufacture, sell, and support both Hitachi and former IBM disk drive products such as
Travelstar, Microdrive, Ultrastar, and Deskstar product lines, was then acquired by Western
Digital in 2012, making Western Digital the largest HDD manufacturer.
Form Factors
The cornerstone of the PC industry has always been standardization. With disk drives, this is evident
in the physical and electrical form factors that comprise modern drives. By using industry-standard
form factors, you can purchase a system or chassis from one manufacturer and yet physically and
electrically install a drive from a different manufacturer. Form factor standards ensure that available
drives will fit in the bay, the screw holes will line up, and the standard cables and connections will
plug in. Without these industry standards, there would be no compatibility between different chassis,
motherboards, cables, and drives.
You might wonder how these form factors are established. In some cases, it is simply that one
manufacturer makes a popular product of a particular shape and connection protocol, and others copy
or clone those parameters, making other products that are physically or electrically compatible. In
other cases, various committees or groups have been formed to dictate certain industry standards.
Then, it is up to the companies that make applicable products to create them to conform to these
standards.
Over the years, disk drives have been introduced in several industry-standard form factors, usually
identified by the approximate size of the platters contained inside the drive.
Table 9.1
lists the
various disk drive form factors that have been used in PCs and portables.
Table 9.1. Hard Disk Form Factors
