this file; while I'm here, rework the GIO arbitrator parameter setup to
match more closely what is done by lunix on the same hardware... Finally,
on a tip from Wilbern Cobb, preserve the graphics-related bits of the
GIO arbitrator parameter register from the PROM-initialized settings so
ARCS console on the graphics display works (tested on both my Indy with
Newport and my Indigo2 with XL gfx).
simonb