All Topics  
Disk controller

 

 
   Email Print
   Bookmark   Link
 

 

Disk controller
 
 
  Topics Disk controller Topic Home

The disk controller (or "hard disk controller") is the circuit
Electronic circuit

An electronic circuit is a closed path formed by the interconnection of electronic components through which an electric current can flow. The electronic circuits may be physically constructed using any number of methods....
 which allows the CPU
Central processing unit

A central processing unit is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage....
 to communicate with a hard disk
Hard disk

A hard disk drive , commonly referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on rapidly rotating hard disk platters with magnetic surfaces....
, floppy disk
Floppy disk

A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangle plastic shell....
 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
Modified Frequency Modulation

Modified Frequency Modulation, commonly MFM, is a line code scheme used to encode information on most floppy disk formats, which include the floppy disk formats used in the classic versions of Amiga OS, most CP/M operating system machines as well as IBM PC compatibles running DOS....
 (MFM) controllers were the most common type in small computers, used for both floppy disk and hard disk drives.






Discussion
Ask a question about 'Disk controller'
Start a new discussion about 'Disk controller'
Answer questions from other users
Full Discussion Forum



Encyclopedia


The disk controller (or "hard disk controller") is the circuit
Electronic circuit

An electronic circuit is a closed path formed by the interconnection of electronic components through which an electric current can flow. The electronic circuits may be physically constructed using any number of methods....
 which allows the CPU
Central processing unit

A central processing unit is an electronic circuit that can execute computer programs. This broad definition can easily be applied to many early computers that existed long before the term "CPU" ever came into widespread usage....
 to communicate with a hard disk
Hard disk

A hard disk drive , commonly referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on rapidly rotating hard disk platters with magnetic surfaces....
, floppy disk
Floppy disk

A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangle plastic shell....
 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
Modified Frequency Modulation

Modified Frequency Modulation, commonly MFM, is a line code scheme used to encode information on most floppy disk formats, which include the floppy disk formats used in the classic versions of Amiga OS, most CP/M operating system machines as well as IBM PC compatibles running DOS....
 (MFM) controllers were the most common type in small computers, used for both floppy disk and hard disk drives. Run length limited
Run Length Limited

Run length limited or RLL coding is a Line code technique that is used to send arbitrary data over a Channel with Bandwidth limits. This is used in both telecommunication and storage systems which move a medium past a fixed head....
 (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
Shugart Associates

Shugart Associates was a computer peripheral manufacturer that dominated the floppy disk drive market in the late 1970s and is famous for introducing the Floppy_disk_drive#The_5.C2.BC-inch_minifloppy....
 Systems Interface (SASI) was a predecessor to SCSI
SCSI

Small Computer System Interface, or SCSI , is a set of standards for physically connecting and transferring data between computers and peripheral devices....
.

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 ATA (IDE) and Serial ATA
Serial ATA

The Serial ATA computer bus is a storage-interface for connecting Host adapter to mass storage devices .Conceptually, SATA is a 'wire replacement' for the older AT Attachment standard ....
 for home use. High-end disks use SCSI
SCSI

Small Computer System Interface, or SCSI , is a set of standards for physically connecting and transferring data between computers and peripheral devices....
, Fibre Channel
Fibre Channel

Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the Technical Committee T11 of the InterNational Committee for Information Technology Standards , an American National Standards Institute ?accredited standards committee....
 or Serial Attached SCSI
Serial Attached SCSI

In computing, the data-transfer technology Serial Attached SCSI moves data to and from computer storage devices such as hard drives and tape drives....
.

Disk controller versus host adapter

The correct term for the components that allows a computer to talk to a peripheral bus is host adapter
Host adapter

In computer hardware, a host controller, host adapter, or host bus adapter connects a host system to other computer network and computer storage devices....
 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
Disk read-and-write head

Disk read/write heads are mechanisms that read data from or write data to disk drives. The heads have gone through a number of changes over the years....
 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
Motherboard

A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
'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
Disk array controller

A disk array controller is a device which manages the physical disk drives and presents them to the computer as Logical Unit Number. It almost always implements RAID#Hardware RAID RAID, thus it is sometimes referred to as RAID controller....
 that allows hardware RAID
RAID

RAID is an acronym first defined by David A. Patterson , Garth A. Gibson and Randy Katz at the University of California, Berkeley in 1987 to describe a Redundant Array of Inexpensive Disks, a technology that allowed computer users to achieve mainframe-class storage reliability from low-cost and less reliable PC-class disk-drive componen...
 to be formed. Sometimes it may be even physically integrated with an HBA, but it performs different functions.

See also

  • Forensic disk controller
    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....