The Serial ATA [SATA] bus is the serial version of the IDE [ATA] spec.
Uses a 4 conductor cable with two differential pairs [Tx/Rx], plus an additional three grounds pins and a separate power pin. Data runs at 150MBps [1.5GHz] using 8B/10B encoding and 250mV signal swings, with a maximum bus length of 1 meter . Later enhancements move the data transfer speed to; 300MBps [3.0Gbps], then 600MBps [6.0Gbps]
Serial ATA uses LVDS [EIA/TIA-644] with voltages of 250mV; while parallel ATA is based on TTL signaling. Serial ATA is a point-to-point interface where each device is directly connected to the host via a dedicated link. The Bit Encoding used is: Non Return to Zero (NRZ) encoding for data communication on a differential two wire bus. The use of NRZ encoding ensures compact messages with a minimum number of transitions and high resilience to external disturbance. The termination resistor is 100 Ohms [+/- 5 Ohms] differential.
Serial ATA uses only 4 signal pins, improving pin efficiency over the parallel
ATA interface which uses 26 signal pins going between devices [over an 80 conductor
ribbon cable onto a 40 pin header connector] .