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
