In principle, any PCI device can be supported on an OFW Macintosh, 
provided that the PCI card has an FCode driver on it. One other 
market you can look for PCI boards with FCode drivers onboard is the 
Sun market, since they originated OpenBoot firmware. Whether they 
will work in a Mac depends partly on how well the Fcode on the PCI 
board interacts with Apple's (poor) OpenBoot firmware implementation 
in their early motherboards.

Bear in mind that the FCode drivers on a PCI card are only active 
when the system is booting; once NetBSD starts, there has to be a 
NetBSD driver for the device for it to continue to work (yes, there 
is an exception in NetBSD/ofppc, but let's not go there right now).

What's probably going on with your USB PCI add-in card (no, the S900 
did not have built-in USB) is that it got power from the PCI bus when 
the system was turned on, and did its own basic power-on 
initialization which apparently included putting power on the USB (or 
it could be that the system firmware did basic "PCI card turn-on"). I 
bet your USB mouse did its own power-on initializatiobn when it got 
power from USB.

The question is whether there's an FCode driver on the USB card that 
then registers any USB HIDs as input devices, or mass storage devices 
that can be booted from (USB disks, floppies, CD-ROMs, etc). I bet 
that all you'll see is a PCI ID tuple (vendor ID, product ID) and the 
addresses of the PCI registers, but no other "words" registered by 
the USB card.

	Erik <fair@netbsd.org>