Disk controllers allow CPUs to communicate with disks in a computer. They use interfaces such as ATA, IDE, and SCSI. Basic operations include read and write. Registers are used to specify I/O requests, and device drivers do the mapping. Different types of disk controllers include disk array, HDC, and forensic.
In a computer, the disk controller is a circuit that allows the central processing unit (CPU) to communicate with other disks in the computer, such as a floppy disk, hard drive, or other type of disk drive. Disk controllers use interfaces such as Advanced Technology Attachment (ATA) and Integrated Drive Electronic (IDE), which are used more frequently in personal computers (PCs), and Small Computer System Interface (SCSI), which is used more frequently in computers of ” business class”. Basic disk controller operations include variations on read and write operations. The operating system (OS) of the controller uses numbered blocks while the disk uses other factors including physical cylinder, sector and track numbers to operate. A device driver does the mapping.
The common ATA and IDE interfaces used by disk controllers operate through sets of registers, which are located at various points in the Input/Output (I/O) address. These registers are used for specifying information about separate I/O requests. After writing the device’s “command register,” the disk controller begins performing a requested operation. Some data transfers occur between a computer’s memory and its disk when the designated “data request” bit is set in a status register. This occurs in write operations to a disk controller shortly after a command is issued, and in read operations, a stop command indicates that data is available.
Disk controllers have certain controller registers that perform different functions. In one register, bytes of data are read and written, but commands are set to read or write to a completely different register. Another register is the “error log” which produces code errors. Two registers work together and indicate the cylinder number of a disk controller, while another register indicates a drive or head number. The last two registers are used to indicate the number of sectors to read/write and the sector number.
There are several types of disk controllers that can be components of a computer. One type of disk controller is the disk array controller, which manages the physical disk drive component and presents it to a computer in terms of logical drives. It implements hardware RAID (Redundant Array of Independent Disks) and is often referred to as a RAID controller. The standard Hard Disk Controller (HDC) is an interface that allows computers to read/write information on a hard disk drive (HD). A forensic disk controller is an HDC specialized for gaining read-only access from computers’ HD drives without damaging the contents of its drive.
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