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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Integrated Drive Electronics / AT Attachment (IDE/ATA) Interface | Official IDE/ATA Standards and Feature Sets ]


The original ATA standard defined features that were appropriate for early IDE/ATA hard disks. However, it was not well-suited to support the growing size and performance needs of a newer breed of hard disks. These disks required faster transfer rates and support for enhanced features.

In an ideal world, the standards committee would have gotten the various hard disk manufacturers together to define a new standard to support the added features everyone wanted. Unfortunately, several companies were impatient, and once again started the industry down the road to incompatible proprietary extensions to the original ATA standard. Seagate defined what it called "Fast ATA", an extension to regular ATA, and "Fast ATA-2" soon followed. These extensions were also picked up and used by Quantum. Western Digital, meanwhile, created "Enhanced IDE" or "EIDE", a somewhat different ATA feature set expansion. All of this happened in around 1994.

To try to once again correct the growing confusion being caused by all these unofficial standards, the ATA interface committee created a new, official ATA-2 specification that essentially combines the features and attributes defined by the marketing programs created by Seagate, Quantum and Western Digital. This standard was published in 1996 as ANSI standard X3.279-1996, AT Attachment Interface with Extensions.

ATA-2 was a significant enhancement of the original ATA standard. It defines the following improvements over the base ATA standard (with which it is backward compatible):

  • Faster PIO Modes: ATA-2 adds the faster PIO modes 3 and 4 to those supported by ATA.
  • Faster DMA Modes: ATA-2 adds multiword DMA modes 1 and 2 to the ATA modes.
  • Block Transfers: ATA-2 adds commands to allow block transfers for improved performance.
  • Logical Block Addressing (LBA): ATA-2 defines support (by the hard disk) for logical block addressing. Using LBA requires BIOS support on the other end of the interface as well.
  • Improved "Identify Drive" Command: This command allows hard disks to respond to inquiries from software, with more accurate information about their geometry and other characteristics.

Unfortunately, even after consensus was reached on ATA-2, the old marketing terms continued to be used. Fortunately, all of the drives of this era have now passed into obsolescence, and the hard disk companies are in much better agreement now on what terms should be used to describe the hard disk interface. Although the marketing people keep trying. ;^)

Next: ATA-3

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