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How IDE Controllers Work

        Tech | Buses

IDE Evolution
The birth of the IDE interface led to combining a controller like this one with a hard drive.
The birth of the IDE interface led to combining a controller like this one with a hard drive.

IDE was created as a way to standardize the use of hard drives in computers. The basic concept behind IDE is that the hard drive and the controller should be combined. The controller is a small circuit board with chips that provide guidance as to exactly how the hard drive stores and accesses data. Most controllers also include some memory that acts as a buffer to enhance hard drive performance.

Before IDE, controllers and hard drives were separate and often proprietary. In other words, a controller from one manufacturer might not work with a hard drive from another manufacturer. The distance between the controller and the hard drive could result in poor signal quality and affect performance. Obviously, this caused much frustration for computer users.

IBM introduced the AT computer in 1984 with a couple of key innovations.

  • The slots in the computer for adding cards used a new version of the Industry Standard Architecture (ISA) bus. The new bus was capable of transmitting information 16 bits at a time, compared to 8 bits on the original ISA bus.
  • IBM also offered a hard drive for the AT that used a new combined drive/controller. A ribbon cable from the drive/controller combination ran to an ISA card to connect to the computer, giving birth to the AT Attachment (ATA) interface.

In 1986, Compaq introduced IDE drives in their Deskpro 386. This drive/controller combination was based on the ATA standard developed by IBM. Before long, other vendors began offering IDE drives. IDE became the term that covered the entire range of integrated drive/controller devices. Since almost all IDE drives are ATA-based, the two terms are used interchangeably.


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