Hard disk drives are accessed over one of a number of bus types, including parallel ATA (PATA, also called IDE or EIDE; described before the introduction of SATA as ATA), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel. Bridge circuitry is sometimes used to connect hard disk drives to buses with which they cannot communicate natively, such as IEEE 1394, USB, SCSI, NVMe and Thunderbolt. Show
Disk interface families[edit]Disk drive interfaces have evolved from simple interfaces requiring complex controllers to attach to a computer into high level interfaces that present a consistent interface to a computer system regardless of the internal technology of the hard disk drive. The following table lists some common HDD interfaces in chronological order:
Early interfaces[edit]A data cable (top) and control cable (below) connecting a controller card and an ST-506 type HDD. Power cable not shown. The earliest hard disk drive (HDD) interfaces were bit serial data interfaces that connected an HDD to a controller with two cables, one for control and one for data.[a] An additional cable was used for power, initially frequently AC but later usually connected directly to a DC power supply unit. The controller provided significant functions such as serial/parallel conversion, data separation, and track formatting, and required matching to the drive (after formatting) in order to assure reliability. Each control cable could serve two or more drives, while a dedicated (and smaller) data cable served each drive. Examples of such early interfaces include:
In bit serial data interfaces the data frequency, data encoding scheme as written to the disk surface and error detection all influenced the design of the supporting controller. Encoding schemes used included Frequency modulation (FM), Modified Frequency Modulation (MFM) and RLL[2] encoding at frequencies for example ranging from 0.156 MHz (FM on 2311) to 7.5 MHz (RLL on ST412) MHz. Thus each time the internal technology advanced there was a necessary delay as controllers were designed or redesigned to accommodate the advancement; this along with the cost of controller development led to the introduction of Word serial interfaces. Enhanced Small Disk Interface (ESDI) was an attempt to minimize controller design time by supporting multiple data rates with a standard data encoding scheme; this was usually negotiated automatically by the disk drive and controller; most of the time, however, 15 or 20 megabit ESDI disk drives were not downward compatible (i.e. a 15 or 20 megabit disk drive would not run on a 10 megabit controller). ESDI disk drives typically also had jumpers to set the number of sectors per track and (in some cases) sector size. Word serial interfaces[edit]Historical Word serial interfaces connect a hard disk drive to a bus adapter[b] with one cable for combined data/control. (As for all early interfaces above, each drive also has an additional power cable, usually direct to the power supply unit.) The earliest versions of these interfaces typically had an 8 bit parallel data transfer to/from the drive, but 16-bit versions became much more common, and there are 32 bit versions. The word nature of data transfer makes the design of a host bus adapter significantly simpler than that of the precursor HDD controller.
Several Parallel ATA hard disk drives
Bit serial interfaces[edit]Modern bit serial interfaces connect a hard disk drive to a host bus interface adapter (today in a PC typically integrated into the "south bridge") with one data/control cable. Each drive also has an additional power cable, usually direct to the power supply unit.
An mSATA SSD on top of a 2.5-inch SATA drive
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What two connection types do you use to connect an external hard drive?Despite their size, they can store a large amount of data, including documents, spreadsheets, presentations, music, and videos. Most external hard drives connect to a computer through a USB or eSATA connection, and many also draw power needed to run from the computer's USB port.
What type of connector can be used to connect an external hard drive to the PC motherboard choose two?SATA Cables for HDDs
In a PC setup, SATA cables can be used to connect the hard disk to the motherboard.
What kind of part does an external hard drive typically connect to?An external drive is a hard disk that comes in a case that connects to your computer with a USB cable.
How do I connect an external hard drive?Plug one end of the external hard drive's cable into the USB port. If the cable uses a USB 3.0 connection, it should only fit one way. USB-C connections can be inserted in any way that fits the port. Plug the other end of the cable into your external hard drive.
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