How IDE Controllers Work

For anyone using a computer, storage options offered by the computer are extremely important. These days, several storage options come into to play such as floppy drive, hard drive, CD ROM drive etc. Integrated Drive Electronics (IDE) interface is the means by which any storage device can connect with the computer. Actually IDE was first built for IBM’s AT computer and was named AT Attachment (ATA). However, because of its success and convenience, several other companies adopted this and called it as an IDE.

The reason behind the Development

The main aim behind the development of IDE was to combine the hard drive and the controller, hence standardizing the use of hard drives in a computer. Earlier, every company had a separate hard drive and its controller. Then again, both were set apart so far that this resulted in poor quality of signal and performance. Thus, IDE was conceived so as to simplify the entire process. For those uninitiated, a controller is a small circuit board with chips that looks into guiding the hard drives for storing and accessing data. Most controllers also comprise of a memory helping these towards enhancing the hard drive’s performance.

The Current Scenario

These days, most motherboards comprise of an IDE interface. This interface is also referred to as IDE controller by many; however, this is a wrong usage of the term. This interface is actually just a host adapter aiming towards connecting a complete device to the computer. The actual controller, rather, is placed on a circuit board which is connected to a hard drive. The initial IDE interfaces was aimed at connecting hard drives. However, these days, IDEs have been developed to be used as a universal interface for connecting all possible drives such as floppy drive, CD-ROM, tape back up drives etc to the computer.


The IDE devices are connected by a ribbon cable, where the wires lie next to each other instead of being bungled up or wrapped together. Certain characteristics of the cable are listed below:

• The cable has three keys – blue (attaches to motherboard), black (attaches to primary drive) and grey (attaches to secondary drive).
• One side of the cable comprises of a stripe that tells the user that the wire on this side is attached to Pin 1 of each connector.
• Wire 20, though not connected to anything, ensures that the cable is correctly attached to the drive.
• These days, most manufacturers also use a cable key to ensure that the cable is not reversed. This cable key allows the cable to be attached in one position only.

Now at any given time, one IDE interface can connect two devices. These days, most motherboards come with integrated interfaces of dual IDEs, hence supporting up to four IDE devices. Now there is no separate controller to look into the functioning of these four devices to check if they are communicating with the computer. Nevertheless, the manufacturers decided to get into a master and slave formation in case of multi-connections. They let one drive be called master (primary drive), while the secondary drive was called a slave. The secondary drive will only start functioning once it has ascertained that the primary drive is idle at that moment. In case the primary drive is communicating with the computer, it will tell the secondary drive to wait and give the signal for continuing only once it has completed its transfer. Any drive can become slave or master as and when desired by the manufacturer!

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