Disk controller

Disk controller

The disk controller is the circuit which enables the CPU to communicate with a hard disk, floppy disk or other kind of disk drive.

Early disk controllers were identified by their storage methods and data encoding. They were typically implemented on a separate controller card. Modified frequency modulation (MFM) controllers were the most common type in small computers, used for both floppy disk and hard disk drives. Run length limited (RLL) controllers used data compression to increase storage capacity by about 50%. Priam created a proprietary storage algorithm that could double the disk storage. Shugart Associates Systems Interface (SASI) was a predecessor to SCSI.

Modern disk controllers are integrated into the disk drive. For example, disks called "SCSI disks" have built-in SCSI controllers. In the past, before most SCSI controller functionality was implemented in a single chip, separate SCSI controllers interfaced disks to the SCSI bus.

The most common types of interfaces provided nowadays by disk controllers are PATA (IDE) and Serial ATA for home use. High-end disks use SCSI, Fibre Channel or Serial Attached SCSI.

Disk controller versus host adapter

The correct term for the components that allows a computer to talk to a peripheral bus is host adapter or host bus adapter (HBA). On the other hand, a disk controller allows a disk to talk to the same bus. Those two are often confused, especially in the PC world. In fact signals read by a disk read-and-write head are converted by a disk controller, then transmitted over the peripheral bus, then converted again by the host adapter into the suitable format for the motherboard's bus, and then read by the CPU.

Sometimes there may be yet another controller between a host adapter and a disk controller - a disk array controller that allows hardware RAID to be formed. Sometimes it may be even physically integrated with an HBA, but it performs different functions.

See also

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Disk Controller — Disk Controller,   Controller …   Universal-Lexikon

  • disk controller —    The electronic circuitry that controls and manages the operation of floppy disks and hard disks. A single disk controller may manage more than one hard disk. Many disk controllers also manage floppy disks and compatible tape drives. In the… …   Dictionary of networking

  • disk controller — noun (computer science) a circuit or chip that translates commands into a form that can control a hard disk drive • Topics: ↑computer science, ↑computing • Hypernyms: ↑control, ↑controller …   Useful english dictionary

  • disk controller —    A hardware device that controls how data is written to and retrieved from the disk drive …   IT glossary of terms, acronyms and abbreviations

  • Floppy disk controller — A floppy disk controller (FDC) is a special purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer s floppy disk drive (FDD). This article contains concepts common to FDCs based on… …   Wikipedia

  • Forensic disk controller — A forensic disk controller or hardware write block device is a specialized type of computer hard disk controller made for the purpose of gaining read only access to computer hard drives without the risk of damaging the drive s contents. The… …   Wikipedia

  • 4FDC Floppy Disk Controller — The Cromemco 4FDC Floppy Disk Controller is designed to interface both 5 and 8 inch floppy disk drives to the S 100 computer bus used in Cromemco and other IEEE 696 computers. It also contains an RS232 serial I/O channel with software selectable… …   Wikipedia

  • hard-disk controller —    An expansion board that contains the necessary circuitry to control and coordinate a hard disk drive. Many hard disk controllers can manage more than one hard disk, as well as floppy disks and tape drives. On some PCs, the hard disk controller …   Dictionary of networking

  • Floppy Disk Controller —   [dt. »Disketten Controller«], Controller für das Diskettenlaufwerk, heute meist in dieses Laufwerk integriert. Er steuert vor allem die Zugriffe und die Datenübertragung …   Universal-Lexikon

  • Disk II — drives. The Disk II Floppy Disk Subsystem was a 5¼ inch floppy disk drive designed by Steve Wozniak and manufactured by Apple Computer. It was first introduced in 1978 at a retail price of US$495 for pre order; it was later sold for $595… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”