It's unclear if this was supposed to be a PB or Mac version of the 3940UW, however I was able to get a driver from the mirror site listed above and flash the card with Rom Version 4.1. When installed in the 9600/G4, with no ribbon cable connected, the 9600 will not boot. It gets to the happy Mac and hangs. However, when installed in the 8600/300 (604ev) it works just fine driving a 15K RPM Seagate and a 10K RPM WD. Go figure.

I've punted back to a 2940W in the 9600 and a 29160N in the 8600. If anyone wants this 3940UW they can have it for $10 shipped in the US.

Anyway, thanks for pointing out that I didn't dig deep enough in the Adaptec site.