IDE cables, also known as Parallel ATA cables, are part of an internal device specification set forth by the X3/INCITS committee. These cables are used within the specification to connect devices such as optical drives, hard drives and solid state drives. IDE cables have largely been replaced by the new SATA technology released in 2003.
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The first version of the IDE specification, which maintains the design features of IDE cables, was introduced in a joint venture between the Western Digital, Control Data and Compaq corporations. Compaq was the first manufacturer to feature IDE drives in a product line for consumers, in 1986. This specification was unique in that it not only revamped the connectors and interfaces for the IDE cable, but also placed the drive controller on the hard drive itself. This reduced the amount of traffic over the cable and significantly reduced operation overhead for the drives.
The function of the IDE cable was to act as a medium for data transmission between internal devices, such as hard drives, and the motherboard of the computing solution. Initially, IDE cables were only capable of transfer speeds up to 16 MB/s. This changed as the technology matured, and the final maximum transfer speed of the IDE specification is 133 MB/s. IDE cables are limited by the specification to 18 inches. Due to this limitation, these cables are rarely used for external devices.
The initial cable for the IDE specification was the 40-wire ribbon cable. Each of these cables were wired with either two or three connectors. One connector attached to the system motherboard, while the other attached to a system drive or device. In the case of three connectors, two devices could be attached to the drive end of the cable and share an IDE channel. These connectors were color-coded as blue, black and grey to signify proper connective points.
As the IDE specification grew to encompass ever-increasing transfer rates, the design of the IDE cable had to be restructured. As the transfer speeds increased, the possibility for "cross-talk" increased as well. This is the process of electrical signals on one conductor wire inadvertently affecting the signals on a neighboring wire. In an effort to reduce this cross-talk, the 80-wire IDE cable was released. All of the additional wires were nothing more than ground wires used to add distance between data and signaling wires. 80-wire IDE cables are the current standard for IDE installations as of November 2009.
A separate variant of the IDE cable was designed specifically for use in mobile computing, such as laptops. The 44-wire IDE cable was identical to the 40-wire IDE cable, with a few minor exceptions. The 44-wire IDE cable was designed to be compatible with only 2.5-inch internal drives, such as laptop hard drives. Furthermore, the extra four wires on this specific cable were not used for data, signaling or grounding. These wires were used as power conduits to the devices it served. This allowed for a smaller form factor and negated the need for two separate cables within a laptop for every drive.