Seven-wire data cable. Connectors measure just 8 mm wide.
About Serial ATA
Lower Voltage - Parallel ATA is based on TTL signaling, requiring integrated circuits to tolerate input signals as high as 5 volts. Soon, integrated circuits manufactured on the leading manufacturing processes will not be able to efficiently support 5 volt signaling voltages. With the upcoming fine lithographies, it will not be practical to support 5 volt signaling tolerance. Serial ATA manages this by reducing signaling voltages to approximately 250 millivolts (0.25 volt).
Pin Efficiency - Currently, the parallel ATA interface has 26 signal pins going into the interface chip. Serial ATA uses only 4 signal pins, improving the pin efficiency and accommodating a highly integrated chip implementation.
Improved Cable and Connector Plant - The current parallel ATA cable and connector are bulky, made up of 80 conductor ribbon cables and 40 pin header connectors. Instead, Serial ATA uses a much smaller serial cable similar in appearance to modern telephone cables. Eliminating a cable nest improves system airflow and cooling, and offers greater freedom in chassis design. Serial ATA also improves manufacturability and ease of use by allowing better connector and cable design.
Master-Slave Interaction - With today's parallel ATA implementation, pairs of devices share a common cable in a master-slave relationship, resulting in available bandwidth being shared between the devices. Also, since devices on the cable interact, they must be jointly qualified, resulting in substantial expansion of the system integrators' qualification matrix in order to comprehend possible combinations of devices. By contrast, Serial ATA is a point-to-point interface where each device is directly connected to the host via a dedicated link. Therefore, each device has the entire interface bandwidth dedicated to it, and there is no interaction between devices. As result, software can be streamlined, eliminating the overhead associated with coordinating accesses between the master and slave device sharing the same cable.
Hot-Plug Opportunity - A benefit of Serial ATA is that it provides the opportunity for devices to be hot-plugged and inserted directly into receptacles, an approach that is not directly supported by parallel ATA. Serial ATA includes all the mechanical and electrical features necessary to allow devices to be directly inserted into receptacles while the system is powered (commonly referred to as "hot-plugged"), and the protocol ensures that device discovery and initialization are handled.