Adaptec 2120s raid card and 8.1?

I see on adaptecs web site this card has been supported since 7.3. But when trying to install 8.1 it finds no disks. I have done nothing out of the norm in the install. Do I need to??? The MB is a Super micro X5ss8-gm that has also an onboard an Adaptec 7902 dual-channel Ultra320 SCSI controller but the disks are connected to the raid 2120s card. Any help appreciated. Regards Mark