Scott, yep, you're right, the 630, and all Macs up to the Beige G3, actually, had SCSI CD-ROM drives (apart from PowerBooks)
Anyway, have a look at the jumpers...the ID that Apple sets the drive to by default is 3, and IIRC, that can be obtained by putting jumpers over the "0", "1" and "2" pins, though I'm at a netcafe now, so I can't check any of mine, sorry.
And the drive should have Termination Power enabled, they shipped from Apple with it enabled. Speaking of which, you might want to double-check the termination of your SCSI chain.
Anyway, have a look at the jumpers...the ID that Apple sets the drive to by default is 3, and IIRC, that can be obtained by putting jumpers over the "0", "1" and "2" pins, though I'm at a netcafe now, so I can't check any of mine, sorry.
And the drive should have Termination Power enabled, they shipped from Apple with it enabled. Speaking of which, you might want to double-check the termination of your SCSI chain.