The specs, SATA 1.0a, and the six post SATA 2.0 extensions, are now collectively called SATA 2.5. SATA 1.0a is an minor addition to SATA 1.0 spec, and as with most things with an 'a' extension, it cleans up problems at 1.0. The post 2.0 specs are a little more interesting.
The first of these is called SATA Extensions, and they entail a lot of things like NCQ and performance enhancing technologies. The next two are called Cables and Connections Volume 1 and 2. 1 deals with internal connectors, those little engineering diagrams that people's eyes glaze over when they read how many mm away from a edge a pin must be. Volume 2 takes the fun to external cables, eSATA and other similar things. Party time here let me tell you.
The next spec is Port Multiplier, it allows you to take a single port and chain a few more, usually four, off of it. Think the old PATA cable with a second port, but this time on a circuit board. On a similar note, there is a Port Selector spec. This allows you to have multiple paths to the same device for failover and enterprise apps. If you need this, you really need it, but most people can get by with just one path. Finally there is a Phy spec.
So, all seven of these pieces are out and in use now, called have been rolled into SATA 2.5. You probably have one or two if you have bought a SATA drive recently, and Intel's ICH7 southbridge supports much of it, as so many SATA 2 devices. One thing to realize though is that many of the specs are optional, and others are just not relevant in many situations. A controller does not care about a cable spec, and an external connector does not relate much to a drive.
When you see a SATA 2.5 logo'd device, you won't necessarily get more than a 2.0 device. For vendors, it makes life a little easier, they can ask about one spec instead of seven. For device manufactures, it is a single coherent convention that comes in one package. This makes their life easier for them, and that is the purpose of the new SATA 2.5.µ
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