Unfortunately, that device wasn't supported in X11R5.  Actually, you
can be a guinea pig for me next time I have a chance to build a new
kernel - I'd like to know if the new console code I hacked works okay
on the mfb device.

The Xcfbpmax code might sort of work if you kludge up a /dev/pm that
actually points at the mfb device (see arch/pmax/pmax/conf.c for the
major number), but I wouldn't want to make any promises about it.

			       _MelloN_