Integrated Drive Electronics (IDE) is really a misnomer in the way we use it today. IDE really refers to any drive with the controller built-in. The interface most of us use, that we call IDE, is actually called ATA, or AT Attachment.

Most drives today are IDE. These drives have the controller built on. They plug into a bus connector on the motherboard or 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. Lastly, integrating the controller is easier on the manufacturer because they do not have to worry about complying with another manufacturer’s controller. Each drive is an independent entity.

The IDE specification has evolved quite a bit since it was first released in the 1980’s. It is short for Integrated Drive Electronics. ATA, or AT Attachment, also goes hand-in-hand with IDE, since they are basically the same concept. The basic concept is that the drive’s controller is integrated onto the device itself rather than having a separate controller. This reduces cost and also makes firmware updates easier since there is no cross-manufacturer complexity. While ATA refers to the 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 extention 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 natievely supported by IDE without drivers.

The Original IDE/ATA

CDC, Compaq, and Western Digital were the first to create the interface. They also decided to use the 40-pin connector. They were large drives of the 5.25″ form, but were only 40M. They were used in the early Compaq 386 systems, using WD controllers. Later, Compaq founded Conner. 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 manufacturer’s 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 us 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, then, require a program tailored to drives from a certain manufacturer, one that knows that company’s commands.

Non-Intelligent IDE was the first type. These drives were simplistic. They only responded to the first eight commands built into the original WD1003 controller. They were actually more like ST506.412 drives with the controller screwed on. Most of these drives could be low-level formatted, unlike today’s drives. Each was low-level formatted in the factory with a few optimizations built on. Factory defects were written as a file to the drive. This means that, although you can low-level format the drive, it would erase the factory optimizations and defect list. Some companies released programs to do this while saving these settings, but many did not.

Dual Drives

Using two drives in the same system has been known to be hard at times. This is usually due to the fact that each drive has its own controller, both trying to operate over the same bus. One of the nice features introduced with ATA 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 a jumper 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 itself. This is done with that jumper. Setting the drive as either master or slave tells it to ignore the commands for the other drive and to only act on ones meant for itself.