There are two categories of hard drive connections. The first type are power connections which supply device specific voltages to power the hard drive, both electronically and mechanically. The second type are data connections, which serve to connect the hard drive to the motherboard's chipset through a data bus. There are also hard drive planes which combine both for various reasons.
The established power connector for PATA, Parallel ATA or EIDE, and some budget SCSI, Small Computer System Interface, drives is the Molex connector. This connector was first pioneered by the Molex corporation, and remained the standard for device power connectors until the advent of the SATA specification. These connectors provide two voltage rails, 12 Volt and 5 Volt, and two ground rails. These connectors are keyed to prevent improper insertion, and are virtually always a translucent white color.
Parallel ATA Data Connector
PATA drives use a flat ribbon style connector to interface between the computer's motherboard and physical disk. This ribbon contains 80 wires, as of the current 2009 specification revision, which support up to two devices per cable. This interface is also used widely with most non-SATA optical drives. The PATA ribbon cables are usually grey with one blue connector for the motherboard interface, one grey connector that provides secondary device connections, and one black connector for primary device connection. The ribbons may be up to 18 inches in length.
SATA Power Connector
The SATA, Serial ATA, power connector, is the successor to the Molex power connector ever since its release in 2003. The SATA power cable is a 15 pin connector that is built on a slim wafer design to prevent improper installation. The SATA power connector does not, unlike the Molex connector, rely on friction to stay securely attached. Rather, it has a quick release push lever to hold it in place and facilitate quick release. This was seen by the market as a welcome improvement, as Molex connectors were often difficult to remove from their sockets.
SATA Data Connector
The SATA data connector is also a wafer connector which calls for seven connective wires, three for ground and four for data. Unlike Molex connectors, the SATA cables can only support one device per channel. However, these cables are much smaller in size and cylindrical in shape. These connectors are also keyed for device damage prevention, and can be in lengths of up to 3.3 feet. These connectors also have a push button lock-in holding system. The most common colors for these cables are red cords with black connectors.
Plane connectors are solid state connectors which combine the power and data interfaces into one physical connector. This can be advantageous in an area with tight space, as it allows for cables to be more easily directed away from hot components. The most common applications for plane connectors is within enterprise server chassis and laptop computers. Both of these computing solutions have very little free space available, and require hard drive maintenance to be as streamlined as possible. Plane connectors require that a drive merely be pushed against it in the correct orientation to be operational.
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