Asus P6X58D Prem. doesn't detect SATA 3 HHD

I am trying to install a WD2002FAEX SATA 3 HD in my Asus P6X58D Premium motherboard. The specs say it has 2 SATA 6.0 Gb/s interfaces but the bios does not detect the drive. However, when I connect to a SATA 3.0 Gb/s interface the drive works fine.

I am still at bios version 1201 and would want to avoid a bios upgrade if I don't need it.

Is there a way to get the drive to work at 6 Gb/s? Is there any advantage?

My build includes

CPU Intel i7-950 (no overclocking)
Mem 8 G
OS Windows 7 Home Premium (64-bit)

TIA