hard disk of computer


Hard disks provide fast retrieval because they rotate constantly at high speed, from 5,000 to 15,000 RPM. Either to preserve battery life in laptops or to promote longevity, hard disks can be configured to turn off after a defined period of inactivity.
It Started in the Mid-1950s
In 1956, IBM introduced the RAMAC hard disk with platters two feet in diameter that held the equivalent of 100,000 bytes. In the 1980s, desktop computer hard disks were introduced with 5MB using 5.25″ platters (see ST506). Today’s entry-level drives have at least 8,000 times more capacity. Platter size was reduced to 3.5″ for desktops, 2.5″ for laptops and 1″ for handhelds. In 2004, Toshiba introduced the 0.85″ drive (see below). See magnetic disk, floppy disk, Microdrive, drop protection and CAV.
TYPES OF HARD DISKS
Transfer
Type of Encoding Rate Range of
Interface Method** (Per sec) Capacities
SATA (IDE) RLL 150-300MB 40GB-1.2TB
PATA (IDE) RLL 3-133MB 500MB-400GB
SCSI RLL 5-320MB 20MB-300GB
Older Interfaces
IPI RLL 10-25MB 200MB-3GB
ESDI RLL 1-3MB 80MB-2GB
SMD RLL 1-4MB 200MB-2GB
IDE RLL 1-8MB 40MB-1GB
ST506 RLL RLL 937KB 30MB-200MB
ST506 MFM 625KB 5MB-100MB
Most disks use RLL, but encoding methods are not prescribed by all interfaces.
A few of the top Hard Disk manufacturing companies include: Western Digital, Seagate, Samsung, Fujitsu, Maxtor, Toshiba, Quantum, Conner, NEC, Micropolis and Toshiba. A few of these companies only make notebook hard drives.