What is SATA II? How is it different from SATA "one"? Should I care if my system supports SATA II?

Computer Technology Review, Feb, 2005 by Conrad A. Maxwell

In summary, if you are concerned with the power issue, use this feature.

When Do I Need a Port Selector?

The port selector is the flip side to the port multiplier--instead of supporting multiple drives, the port selector supports multiple host controllers for controller redundancy. If one host controller fails, the other one can take over without missing a step. This feature is for advanced system design where a protected performance array is not enough reliability.

In summary, if you need ultra reliability and cost is not the issue, then a port selector is just what you need.

Should I Design in an eSATA port?

The expanded electrical specification for the Serial ATA physical layer (PHY) was written to improve on first generation PHY designs and lengthen the cable distance between transmitter and receiver. The original 1.5Gb/s Serial ATA 1.0a, or Gen li, has a maximum length of 1 meter internal cable, and so does the second generation 3.0Gbp/s or Gen2i. The expanded specifications, called Gen1m and Gen2m, are targeted at "short" backplane and External Desktop Applications. These "m" level PHYs have modified transmitter and receiver differential swing specifications. Minimum transmitter amplitudes are increased and minimum receive amplitudes are decreased in order to accommodate additional cable lengths of approximately 2 meters with backward compatibility for Gen li devices. Most motherboards do not support this expanded PHY level and an aspter card will be needed to add a port for this purpose. The SATA IO group calls the m PHY "eSATA," which means an external SATA port.

Today, the only methods for attaching a computer or consumer electronics device to an External Serial ATA storage device is via the Firewire (1394), or USB interface, using bridge ASICs. The problem with this approach is that the Serial ATA signals need to be converted or encapsulated within the USB or Firewire (1394) protocols, resulting in unnecessary cost and reduced performance. Removing signal conversions for External Serial ATA provides the lowest cost and best performing solution to connect to an External Serial ATA storage device. Beyond lower price and higher performance, the average workstation, desktop pc, or consumer device, do not provide sufficient drive bays, large enough power supplies, or adequate cooling to support a robust internal storage system. The only answer is to use external storage upgrade box(es), typically connected by USB or 1394. These older connection devices are as much as 6 times slower than an external SATA box.

In summary, this direct connection provides the opportunity for Desktop, Workstation, or Consumer Devices to add Gen 1m ports on the external skin of every PC, allowing for low-cost, high-performance, easy upgrades. See the SATA IO site for more on this: www.sata-io.org/featureofmonth.asp.> Can I Utilize an xSATA port?

The final part of the expanded electrical specification, Gen 1x and Gen 2x, offers extended length (approximately 8 meters) based on the Serial Attached SCSI Electrical specifications (SAS). This level of PHY signal is not backward compatible, and careful attention to drive and host signals are needed.