thanks again
I've set each of them to 1+0, and get the full capacity for both drives.
Option where - in Promise BIOS ? Don't think so - the only option is RAID ("performance" or "security") or not RAID (then, as I said, the disks don't appear to mboard BIOS.
I'm going to have another look at this tonight.
Can't seem to get the definitive answer for the P4PE (have posted on a few forums, and just emailed Promise, haven't got serial number of mboard to hand so can't email Asus at moment) - whether I can use these SATA drives in non-RAID mode ?