I've got the p5K Dlx.
And the manual's not worth a w***! lol!
by pressing ctrl-i at post i've joined the two drives as a RAID0 (not in manual)
Also in the SATA Configuration menu, it's showing Intel Robson Technology which, according to the manual, it shouldn't be showing at all, as 'configure SATA as' is set to RAID!?!