SATA Revision 2.0 (SATA 3Gb/s)
First-generation SATA devices often operated at best a little faster than parallel ATA/133 devices. Subsequently, a 3 Gbit/s signaling rate was added to the physical layer (PHY layer), effectively doubling maximum data throughput from 150 MB/s to 300 MB/s.
For mechanical hard drives, SATA 3 Gbit/s transfer rate is expected to satisfy drive throughput requirements for some time, as the fastest mechanical drives barely saturate a SATA 1.5 Gbit/s link. A SATA data cable rated for 1.5 Gbit/s 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.
Given the importance of backward compatibility between SATA 1.5 Gbit/s controllers and SATA 3 Gbit/s devices, SATA 3 Gbit/s autonegotiation sequence is designed to fall back to SATA 1.5 Gbit/s speed when in communication with such devices. In practice, some older SATA controllers do not properly implement SATA speed negotiation. Affected systems require the user to set the SATA 3 Gbit/s peripherals to 1.5 Gbit/s mode, generally through the use of a jumper, however some drives lack this jumper. Chipsets known to have this fault include the VIA VT8237 and VT8237R southbridges, and the VIA VT6420, VT6421A and VT6421L standalone SATA controllers. SiS's 760 and 964 chipsets also initially exhibited this problem, though it can be rectified with an updated SATA controller ROM.
SATA Revision 3.0 (SATA 6Gb/s)
Serial ATA International Organization presented the draft specification of SATA 6 Gbit/s physical layer in July 2008, and ratified its physical layer specification on August 18, 2008. The full 3.0 standard 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 Disk drives have already saturated the SATA 3 Gbit/s limit at 250 MB/s net read speed. Ten channels of fast flash can reach well over 500 MB/s with new ONFI drives, so a move from SATA 3 Gbit/s to SATA 6 Gbit/s would benefit the flash read speeds. As for the standard hard disks, the reads from their built-in DRAM cache will end up faster across the new interface. Seagate was the first company to offer SATA 6 Gbit/s hard drives.
The new specification contains the following changes:
A new Native Command Queuing (NCQ) streaming command to enable Isochronous data transfers for bandwidth-hungry audio and video 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.
The enhancements are generally 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.
There's the difference.
)
