I dug out an old IEEE 1394-1995 Dual Firewire card-bus that I used to use with my G3 Pismo and tried it with my G4 Ti PowerBook.
It mounts on the desktop but doesn't seem to work in terms of connecting to any drives.
The Card-bus claims to not need any drivers under Mac OS9 and I certainly don't recall needing to add anything extra on the Pismo, just plug and play (was a long time ago though...)
Under the System Profiler it sees it as:
Card name: cardbus
Card model: TXN,PC11410-02
Crad ROM#: Not Available
Card Revision: 2
Card Vendor ID: 104C
"Compliant with IEEE 1394-1995, 1394a-2000 and OHCI standards"
Are there any specific Extensions that need to be "on" or added to get these things to work?