Parallel ATA interface

Parallel ATA cables transfer data 16 bits at a time. The traditional cable uses 40-pin connectors attached to a ribbon cable. Each cable has two or three connectors, one of which plugs into an adapter interfacing with the rest of the computer system. The remaining connector(s) plug into drives.

ATA's cables have had 40 wires for most of its history (44 conductors for the smaller form-factor version used for 2.5" drives — the extra four for power), but an 80-wire version appeared with the introduction of the Ultra DMA/33 (UDMA) mode. All of the additional wires in the new cable are ground wires, interleaved with the previously defined wires to reduce the effects of capacitive coupling between neighboring signal wires, reducing crosstalk. Capacitive coupling is more of a problem at higher transfer rates, and this change was necessary to enable the 66 megabytes per second (MB/s) transfer rate of UDMA4 to work reliably. The faster UDMA5 and UDMA6 modes also require 80-conductor cables.

July 7, 2011

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