> First, let me give some information about this card.Here's what it says
> on the biggest chip on the card.
> 
> S9530BDC4
> PATENTED
> (c)(m) 1993
> DP83934CVUL-20
> TM
> SONIC-T

That's definitely a Sonic of some sort.

> I've been informed that the card is PDS.

Yes.  Sure sounds like it.

> The device is detected in NetBSD as sn0, but when I try to load the
> device with `ifconfig sn0 up 192.168.0.4`, it freezes and I'm forced to
> reboot.

OK.  Half-good.  It sounds like the interrupts aren't being handled
properly.  This may be because the card isn't being set up properly
somehow.

I don't have time to look into it now, but the first place I'd look is
to be sure that the memory/register setup is being properly configured.
Some Sonic devices are 16-bit and some are 32-bit.  Make sure that that
sort of thing is correct.  Double check the MAC address that was
reported during boot and make sure that it's correct, too.

-allen