The advertised transfer rates on this model drive are between the 1 and 2 terr drives of the same interface- that much I did find out. Actually, the numbers are somewhat interesting. Taken from a WD document copyrighted 2010, the "data transfer rate (max) | host to/from drive (sustained)" for the black series are;
2T (sata 3G) 138MB/s
1T (sata 6G) 126MB/s
1T (sata 3G) 106MB/s
750G(sata 3G) 106MB/s
640G(sata 6G) 126MB/s
640G(sata 3G) 113MB/s
500G(sata 3G) 113MB/s