What's in a name? SATA II Misconceptions
 

Recently Purav and I had the opportunity to work with some retail "SATA II" drives as part of some upcoming articles. Even though we have known about SATA II for well over a year now, seeing retail drives has been really refreshing as Western Digital, Samsung and Hitachi all have units available [RTPE: "SATA II"]. However, the real surprise to us came when the majority of SATA II drives available right now are not capable of 3.0Gbps transfer speeds and others don't claim support for features we almost take for granted; like NCQ. The original SATA standard - usually referred to as SATA, U150, SATA150, or SATA I - gave us a peak transfer rate from the HDD interface to the system bus of about 1.5Gbps. Many believe that if SATA I drives have transfer rates of 1.5Gbps, then 3.0Gbps rates must be held by drives which have SATA II in their names. This is definitely not the case

http://www.anandtech.com/storage/showdoc.aspx?i=2450