On Thu, 4 Mar 1999 22:22:00 +0100 (MET) 
 Anders Magnusson <ragge@ludd.luth.se> wrote:

 > Not likely :-) but maybe the page tables that maps the framebuffer
 > gets paged out. 

Well, more like devices aren't really "wired" memory.  The pmap is allowed
to forget those mappings at any time, as it sees fit.

Say, for example, a process which has mapped the frame buffers is _swapped_
out.  The Alpha pmap will then free all of its page tables.  You need to be
able to reestablish the mapping for individual pages later, when that process
runs again.

        -- Jason R. Thorpe <thorpej@nas.nasa.gov>