It's an ST15150N. I've tried jumpering termination enable alone, term power from drive alone, and both together with no luck. Also, a drive that works fine at chain end in the 8600 exhibits the same problem in the 9500. I tried a different ribbon cable in the 9500, no change.

The drives all spin up and sound like they're being accessed until the happy mac then silence. The CD drive does not appear to be terminated.