|An informational and technical guide to selecting the best hard drive for building a new computer or upgrading a current system.|
IDE Hard Drive Technical Information
Integrated Drive Electronics (IDE) refers to any drive with the controller built-in (integrated) into the disk. Although it really refers to a general technology, most people use the term to refer the ATA specification, or Advanced Technology Attachment.
There are several versions of ATA, all developed by the Small Form Factor (SFF) Committee:
IDE Hard Drives in Computers Today
Most hard drives in computers today are IDE. These hard drives have the controller built-in and do not require a separate interface card. They plug into a bus connector on the motherboard (or sometimes an adapter card). Such drives are easy to install and require a minimum number of cables. This is due to the fact that the controller is on the drive itself. Less parts are needed and the signal pathways can be much shorter. These short signal pathways improve reliability of the drive. Before, data could lose its integrity while traveling over cheap ribbon cables. Also, integrating the controller is easier to manufacture because they do not have to worry about compatibility issues with another manufacturer's hard drive controller. Each hard drive is an independent entity.
While ATA refers to the hard drive itself and how it operates, IDE refers to the type of interface connector (40 pin in this case) as well as the type of controller.
ATAPI, or ATA Packet Interface, is an extension of IDE which allows devices such as CD-ROMs to operate using the IDE standard. It allows such devices to connect directly to an IDE port, although a device driver is needed to make it work, whereas a hard drive is natively supported by IDE without drivers.
The Origin of the IDE/ATA Interface
CDC, Compaq, and Western Digital were the first to create the IDE/ATA hard drive interface. They also decided to use the 40-pin connector. The original hard drives were large drives of the 5.25" form factor, but were only 40 megabyte. They were used in the early Compaq 386 systems, using Western Digital controllers. Later, Compaq founded Conner hard drives. Conner produced drives for Compaq, but was later sold. In the late 1980's, the ATA IDE was set as ANSI standard. This caused all manufacturers to agree with a common design for the interface. But, before this was done, many companies had produced their own variations. This sometimes makes it hard for computer troubleshooters to make these older drives work with newer ones in the same system. Some areas of the ATA standard were left open to manufacturer's for their own commands. Due to this, the standard is really loosely set. Low-level formatting drives require a program tailored to hard drives from a certain manufacturer, one that knows that company's commands.
Dual IDE Hard Drives
Using two drives in the same system with the original specification was known to be hard at times. This is usually due to each hard drive having its own controller, and both trying to operate over the same bus. One of the nice features introduced with ATA specification was the ability to operate two drives together in a chain. The primary drive is the master, and the second drive is the slave. On most drives, you tell it to be a master or a slave with jumper settings on the drive itself. When two drives are on the same ribbon cable, all commands are received by both controllers. Each drive must respond only to commands meant for it.