Difference is at rate they do transfer - bigger sata number denotes faster transfer speed
SATA Revision 1.0 (SATA 1.5 Gbit/s)
First-generation SATA interfaces, now known as SATA 1.5 Gbit/s, communicate at a rate of 1.5 Gbit/s. Taking 8b/10b encoding overhead into account, they have an actual uncoded transfer rate of 1.2 Gbit/s (150 MB/s). The theoretical burst throughput of SATA 1.5 Gbit/s is similar to that of PATA/133, but newer SATA devices offer enhancements such as NCQ, which improve performance in a multitasking environment.
During the initial period after SATA 1.5 Gbit/s finalization, adapter and drive manufacturers used a "bridge chip" to convert existing PATA designs for use with the SATA interface.[citation needed] Bridged drives have a SATA connector, may include either or both kinds of power connectors, and, in general, perform identically to their PATA equivalents. Most lack support for some SATA-specific features such as NCQ. Native SATA products quickly eclipsed bridged products with the introduction of the second generation of SATA drives.
As of April 2010 mechanical hard disk drives can transfer data at up to 157 MB/s,[7] which is beyond the capabilities of the older PATA/133 specification and also exceeds a SATA 1.5 Gbit/s link.
SATA Revision 2.0 (SATA 3 Gbit/s)
Second generation SATA interfaces running at 3.0 Gbit/s are shipping in high volume as of 2010, and prevalent in all[citation needed] SATA disk drives and the majority of PC and server chipsets. With a native transfer rate of 3.0 Gbit/s, and taking 8b/10b encoding into account, the maximum uncoded transfer rate is 2.4 Gbit/s (300 MB/s). The theoretical burst throughput of SATA 3.0 Gbit/s is roughly double that of PATA/133. In addition, SATA devices offer enhancements such as NCQ that improve performance in a multitasking environment.
All SATA data cables meeting the SATA spec are rated for 3.0 Gbit/s and will handle current mechanical drives without any loss of sustained and burst data transfer performance. However, high-performance flash drives are approaching SATA 3 Gbit/s transfer rate, and this is being addressed with the SATA 6 Gbit/s interoperability standard.
SATA Revision 3.0 (SATA 6 Gbit/s)
Serial ATA International Organization presented the draft specification of SATA 6 Gbit/s physical layer in July 2008,[8] and ratified its physical layer specification on August 18, 2008.[9] The full 3.0 standard (peak throughput about 600 MB/s (10b/8b coding plus 8 bit to one byte, without the protocol, or encoding overhead) was released on May 27, 2009. While even the fastest conventional hard disk drives can barely saturate the original SATA 1.5 Gbit/s bandwidth, Solid-State Drives have already saturated the SATA 3 Gbit/s limit at 285 MB/s net read speed and 250 MB/s net write speed with the Sandforce 1200 and 1500 controller. However SandForce SSD controllers scheduled for release in 2011 have delivered 500 MB/s read/write rates, and ten channels of fast flash can reach well over 500 MB/s with new ONFI drives – a move from SATA 3 Gbit/s to SATA 6 Gbit/s allows such devices to work at their full speed. As for standard hard disks, the reads from their built-in DRAM cache will end up faster across the new interface.SATA 6 Gbit/s hard drives and motherboards are now shipping from several suppliers.
The new specification contains the following changes:
6 Gbit/s for scalable performance when used with SSDs
Continued compatibility with SAS, including SAS 6 Gbit/s. "A SAS domain may support attachment to and control of unmodified SATA devices connected directly into the SAS domain using the Serial ATA Tunneled Protocol (STP)" from the SATA_Revision_3_0_Gold specification.
Isochronous Native Command Queuing (NCQ) streaming command to enable isochronous quality of service data transfers for streaming digital content applications.
An NCQ Management feature that helps optimize performance by enabling host processing and management of outstanding NCQ commands.
Improved power management capabilities.
A small low insertion force (LIF) connector for more compact 1.8-inch storage devices.
A connector designed to accommodate 7 mm optical disk drives for thinner and lighter notebooks.
Alignment with the INCITS ATA8-ACS standard.
In general, the enhancements are aimed at improving quality of service for video streaming and high-priority interrupts. In addition, the standard continues to support distances up to a meter. The new speeds may require higher power consumption for supporting chips, factors that new process technologies and power management techniques are expected to mitigate. The new specification can use existing SATA cables and connectors, although some OEMs are expected to upgrade host connectors for the higher speeds. Also, the new standard is backwards compatible with SATA 3 Gbit/s.