Much later as it turns out ...

After a hiatus of several years ... time for an update on this saga.
Got back into this about a week or so ago.
Somewhere along the way the Tiger installation got pooched so had to reinstall.
Somehow managed to do that and get it updated via Software Update to 10.4.11.
Made another attempt to install 10.4 on another partition and it failed.
Had all sorts of problems with the ATTO card initially. Computer would not boot into either OS 9 or OS X unless something was attached to the card.
Once I did attach a 4 bay Fast and Wide external cabinet with 4 IBM drives inside it, the computer did boot up (into both OS 9 and OS X) … but the ATTO card refused to see the drives.
Swapped out the ATTO card for an Adaptec Power Domain 2940UW, booted into OS 9 … and immediately all drives showed up … which allowed me to format and wipe them.
Swapped out the PRAM battery with another one I had on hand since the computer kept losing it’s Time and Date setting every time I disconnected power. Turns out the replacement battery was dead as well.
Ordered some new PRAM batteries from the Borg and stuck a new fresh one in yesterday after checking it with a multimeter.
Once that was done I hooked up the VXA tape drive to the ATTO card and the Sony SDT-9000 DAT to the external bus on the 9600 and attempted to do a couple of restores using Retrospect 5 using both devices.
That resulted in hard lockups of the computer every time I tried it.
At that point I had finally had enough and pulled the Sonnet G4/450 processor card out and swapped in the original Apple 350 MHz “High Performance Processor Card” that came with the machine.
Did two restores totaling about 35 GB from three different VXA tapes which proceeded flawlessly.
I did also try a restore over the network to a 240 GB partition on an SSD in the G5 that I had mounted on the 9600 desktop … but it failed after some time, with Retro complaining that it had trouble writing to the drive.
Since then I have managed to restore (I think) all tape backups on VXA and DAT ... probably over 20 tapes total ... although I do have another 20 or so in the archives I need to check. Both tape drives seem to be working flawlessly ... in OS 9 with the original processor card installed.
Looking like it is going to be an “OS 9 only” machine at this point. And that's fine.
Although I may give OS X another whirl with the other Sonnet processor card just to see if it was something specific to that card ...
