SATA Cable Information

The SATA specification, released in 2002, ushered in a new era of drive transfer speeds and connectivity. This specification utilized a new cabling scheme which provided for much easier system design when considering thermal factors, cabling routes and space requirements. Overall, there were virtually no drawbacks when compared to the earlier EIDE ribbon cables of the previous drive specification.

Cable Length

The SATA specification allowed for considerably longer cable lengths than the EIDE standard before it. The SATA cable allowed for lengths of up to 1 meter, 3.3 feet, whereas the EIDE cable was limited to just 18 inches. This improvement later allowed for larger system chassis to be designed as well as the implementation of a new external specification using the SATA protocol as its cabling medium, instead of USB or fire wire.

Cable Size

The SATA specification calls for a cable with seven conductors, three ground wires and two pairs for data transfer. This is a large miniaturization when compared to the EIDE standard of 80 wires required. Further, the cable itself was many times smaller in overall width due to its modular design. This change became of great importance as airflow within computer chassis has become a very important consideration given today's devices which produce large volumes of heat.

Cable Construction

Unlike the EIDE cables that used a flat ribbon, the SATA specification called for two pairs of twisted data conductors. This design specification is important because the twisted pair implementation reduces the "noise" or cross-talk between the data circuit's wires. This improvement of noise-to-signal ratios allowed for much higher transfer speeds to be realized when the standard was officially implemented and released. These cables also utilized a differential signaling technology that sent the data to be transferred across the data circuits in a predetermined manner to limit noise. This is the reason they have two pairs of data conductors.

Locking and Blade Connectors

Due to their smaller size, a major concern expressed toward the SATA cable was that of accidental unplugging. To counter this concern, the cables are designed with a locking notch just after the seventh conductor. This locking notch allows for a safe and secure means to keep the cable connected. Further, this locking connector has been designed into "blades" that combine the power and data cable into one solid connector, which is secured through a locking notch on each connection. These are most often used on blade servers in which space for cabling is at a priority.

Hot Swapping

One of the most anticipated advantages of SATA cables was the ability to "hot swap." With previous cabling and drive protocols you were required to power down your machine in the event of a drive installation or removal. With the SATA cabling and protocol, however, utilizing "blade" connectors you can simply unplug or plug in a SATA drive and receive 100 percent operation without a restart. The only requirement for this feature is that your SATA controller support the AHCI, or advanced host controller interface specification. This specification is standard in virtually all drive controllers as of late 2009.

References

• Hitachi: Serial ATA - Next Generation Storage Interface
• The Serial ATA International Organization
• Hardware Secrets: Everything You Need to Know About Serial ATA by Gabriel Torres