Date: Tue, 31 May 1994 10:39:45 +0200 (MET DST)
From: Alexander Kjeldaas <astor AT alkymi DOT unit DOT no>
Subject: Page switching on graphics cards
To: Mailing List DJGPP <djgpp AT sun DOT soe DOT clarkson DOT edu>


Would it be possible to hack the code that switch pages on graphics card
in such a way that it would be possible to use rep movsd and things like
that across page boundaries. It seems that the problem is that a movsd or
movsw can be unlucky so that parts of the word is on one side of the page
limit, and another part is on the other side. To solve this problem,
couldn't we make the paging code in the graphics drivers check the upcode
of the instruction that caused the page fault and 'help' it by splitting a
movsd or movsw into mov <byte> instructions?

I guess non aligned movsw instructions are inefficient to use, but if the
paging mechanism would work for all kinds of instructions there would
probably be code that could be optimized because one wouldn't have to be
so 'careful' and always use movsb. 

*ALEX*