I am having trouble with SCSI devices on my Power Center. I am contiuously reseting my pram after I mount a drive using HDTK. I am currently trying to install a 9 gig compaq drive in it. I had similar problems using the computer with a laptop in SCSI mode.
I'm wondering if the SCSI Controller is shot. Try a smaller Hard drive (SCSI) and see if that works. Or better yet, a SCSI Zip or Jazz drive and try to boot off of that. (I recommend the Jazz.) It can be on either the internal or external Chain.
I can confirm that the scsi controller works. I was messing with the HD later and finally got the computer to boot off of it. I didn't have the installer disk, so I was going to copy the System Folder from its previous HD (500mb) and ran into the same trouble I had before of the drive not automounting (it is set to do so). They are on seperate IDs, I wonder if it has something to do with the SCSI timer hingy apple has an update for.