> everything goes fine, I get into the shell prompt, and then when
> `ifconfig bm0 192.168.1.2' is invoked, it just crashes completely

There's a problem with the bm driver (or more likely with the pci or
obio code) that makes bm not work if you didn't netboot. There's a
workaround for it in -current. I believe it should be in both the 0620
snapshot and 1.4.1.

If you want to stick with 1.4, you should be able to make it work by
trying to netboot from Open Firmware before you boot normally. (It
doesn't matter that it fails, IIRC.)

-- Dan