Booting from an install-CD for Beos 4.5 and another one for Plan9
with PCI enabled gives an error. It seems that the function
register_ioport_write() is called with an address (-4) outside
of its expected range (0-65535).
It appears that both operating systems implement the procedure
described in the application note at page 204 from the document
"http://www.singlix.org/trdos/PCI22.pdf"; with the special bits
already cleared.
The following quick patch (against CVS 19-05-2004) works for me
in both cases.