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Serial ATA Hard Drive

By Stephen Bucaro

Every desktop computer built since 1993 has used the IDE (Integrated Drive Electronics, later changed to ATA for Advanced Technology Attachment) interface to handle the hard disk. ATA/33 used a 40-wire ribbon cable to transfer data at 33MBps (megabytes per second). At faster speeds than this, crosstalk becomes a problem.

When you increase the signal frequency on a wire, the signal tends to want to "leave" the wire like radio waves, which interferes with the signal on adjacent wires. To eliminate the crosstalk, a wire connected to gound was placed between each signal wire. ATA/66 and higher use an 80-wire ribbon cable.

Motherboard SATA connectors
SATA connectors on Motherboard

New computers will begin using the SATA (Serial ATA) interface to the hard disk. Some new motherboards come with built-in SATA support. The SATA interface does not use a ribbon cable. Instead, it uses a cable similar to a network cable with only seven wires. Whereas IDE/ATA transfered 32 bits of data in parallel, SATA transfers one bit at a time.

Transfering one bit at a time eliminates the crosstalk problem, but requires a much higher operating frequency to achieve the same transfer rate. Serial ATA has a maximum transfer speed of 150 MBps, with speed increases to 600 MBps planned for the future.

SATA cable

SATA uses a seven wire cable. The connectors snap in using a "blade and beam" connection rather than ribbon cable sockets like IDE does. A cable with only seven wires is much easier to install and much more reliable than a cable with 80 wires.

SATA hard drive