The serial ATA has multiple advantages over its predecessor, the three main being its throughput, cable management and hot plug.
The old ATA standard is commonly referred to as parallel ATA (P-ATA).
The first serial ATA models, which appeared in 2003, allow a theoretical throughput of 1.5 Gbit/s, but have been designed to go much faster. The serial ATA II doubles its 3 Gbit/s throughput and then the SATA III appeared in 2009 to 6 Gbit/s.
The theoretical throughput of 1.5 Gbps is 187.5 MB/s; in practice, the 150 MB/s is not exceeded, which is only 17 MB/s more than the fastest parallel ATA : the ATA/133.
The main advantages of SATA compared to PATA :
-PATA shares the same data sheet with another device, potentially reducing the bandwidth of each of 50%
-The SATA tablecloth is much easier to use, and to place, than that of PATA due to its reduced dimensions.
-Parallel buses now have difficulties to increase their throughput due to a problem of synchronizing data rows. The serial ATA uses the new LVDS for signaling.
-For multiple hard drives, in SATA, each disk has the maximum allowed by its standard and that of the controller. The SATA II standard allows the use of port multipliers.
SATA II standards (convenient peak throughput ~ 300 MB/s) and SATA III (convenient peak throughput ~ 600 MB/s) become useful for use between multiple SSDS, whose throughput starts to exceed 400-500 MB/s for high-end models early 2012.