History

• The ATA specification was an extension of the AT specification set forth by Western Digital in a joint venture with the Control Data Corporation and Compaq computers in 1986. As a corollary, the first ATA hard drives were featured in Compaq computers the same year the technology was released. The initial ATA specification has been amended many times by subsequent technology groups worldwide for use with hard drives and optical disc drives.
  
  

ATA Data Interface

• The ATA interface consisted of three key features. The most innovative of these was the inclusion of a hard drive controller directly on the drive housing itself. Before this, the hard drive controller chip was found embedded into a computer system's motherboard. The data interface for the ATA hard drive is a 40-pin male connector found on the rear face of the drive to the left of the power connector. This 40-pin specification allowed for up to two devices to be placed on one physical ATA data cable.
  
  

ATA Electrical Interface

• The electrical interface of the ATA drive is also a male connector which terminates in four pins. These pins include two ground wires and two voltage rails, 5 Volts and 12 Volts. The ATA drive, whether optical or magnetic, used the Molex connector to attach to any ATX compliant power supply. These connectors use friction for connective security and as such have been criticized by consumers for being overly difficult to remove.
  
  

ATA Data Cables

• The ATA hard drive utilized a flat ribbon cable for connectivity to the system motherboard. This ribbon cable came in 40 or 80 wire variants that could support one or two devices per channel, respectively. Each attached device was given a designation as "Master" or "Slave" on the data channel. The ATA ribbon cable has a physical limit of 18 inches in length, which is the biggest contributing factor to the dearth of mainstream external drives based on the ATA interfacing technology.
  
  

Features and limitations

• While the ATA drive remains popular within the computing industry it is not without its drawbacks. The ATA specification did not take into account the growing size of hard drive capacities and as such ran into a physical capacity limitation of 137 GB. This limitation necessitated operating patches to successfully read the entirety of a hard drive with a larger capacity. The ATA specification did, however, come with password protection for administrators of varying levels and, due to its low cost of manufacturing, provided an easy entry point for consumers into hard drive upgrades.