The concept behind IDE is that the hard drive and the controller should be combined. The controller is a circuit board with chips that provide instructions for exactly how the hard drive stores and retrieves data. Most controllers include memory that acts as a buffer zone to enhance hard drive performance.
Most motherboards come with an IDE interface. The interface is sometimes called an IDE controller, which is a false statement. The interface is actually a host adapter, meaning that it provides a way to connect a complete device to the computer. The actual controller is on a circuit board attached to the hard drive.
The IDE interface was originally developed for connecting hard drives; it has evolved into the universal interface for connecting internal floppy drives, cd-rom drives, and tape backup drives. However, IDE is rarely used for attaching an external drive.
IDE standards include:
1. ATA-1 ? Used as master/slave config. Based on subset of the standard ISA 96-pin connector that uses either 40 or 44 pin connectors and cables. In the 44-pin version, the extra four pins are used to supply power to a drive that doesn't have a separate power connector. ATA-1 also provides signal timing for direct memory access (DMA) and programmed input/output functions.
2. ATA-2 ? Upgrade for ATA-1. Transfer rates increased from 4.16mb/s to 16.67mb/s. Provides power management, PCMCIA card and removable device support. Often called EIDE., Fast ATA or Fast ATA-2. Total hard drive size supported increased to 137.4gb.
3. ATA-3 ? Self-Monitoring Analysis and Reporting Technology (SMART) introduced. ATA-3 added pw protection to access drives.
4. ATA-4 ? Ultra DMA supported. AT Attachment Program Interface (ATAPI) standard introduced. ATAPI provides a common interface for cd-rom drives, tape backup, and other removable storage drives. Ultra DMA increased DMA transfer rate to 33.33mb/s. Version also introduced a cable with 80 conductors. ATA-4 is also refered as Ultra DMA, Ultra ATA, and Ultra ATA/33.
5. ATA-5 ? Introduced auto detection of which cable is used: the 40-conductor or 80-conductor. Ultra DMA is increased to 66.67mb/s with use of 80-conductor cable. ATA-5 is also called Ultra ATA/66.
IDE drives use a ribbon cable to connect to each other. Ribbon cables have all the wires laid flat next to each other instead of bunched or wrapped together in a bundle. IDE ribbon cables have either 40 or 80 wires. There is a connector at each end of the cable and another one about two thirds of the distance from the motherboard connector. This cable cannot exceed 18 inches in total length or signal integrity will begin to degrade. The three connectors are usually different colors and attach to specific items:
1. The blue connector attaches to the motherboard.
2. The black connector attaches to the primary drive.
3. The grey connector attaches to the secondary drive.
Along one side of the cable is a stripe. The stripe tells you that the wire on that side is attached to Pin 1 of each connector. Wire 20 is not connected to anything. There is no pin at that position. That position is used to make sure that the cable is attached to the drive in the right position.
A single IDE interface can support two devices. Most motherboards come with dual IDE interfaces for up to four IDE devices. Because the controller is integrated with the device, there is no overall controller to decide which device is currently communicating with the computer. This isn't a problem as long as each device is on a separate interface, but adding support for a second drive on the same cable took some time and effort.
To allow for two drives on the same cable, IDE uses a special configuration called master and slave. This config allows one drive's controller to tell the other drive what to do. The slave will make a request to the master, which then check to see if it's communicating with the motherboard. If it isn't, it tells the slave to go ahead and transmit. If the master is communicating with the computer when the slave makes the request, it tells the slave to wait and then informs it when it's done.
I hope you found this article informative. Feel free to leave any questions or comments.
This article was originally published by CyberArmy.net in the CyberArmy Library.
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