Adaptc 8945 BIOS question.

I have an Adaptec AHA-8945 Firewire/SCSI controller. I also have an Adaptec AIC-7880 SCSI controller built onto a Single Board Computer. I’m unable to boot from the AIC-7880 controller when the AHA-8945 controller is installed. Both controllers workOK under Windows NT 4.0. How can I disable the SCSI portation of the AHA-8945 controller? I can’t seem to be able to disable the BIOS on the AHA-8945 controller. Any suggestions?