Quick reactions on graphics post

[Bill Frantz]

At 9:19 AM -0800 4/30/98, Jonathan S. Shapiro wrote:

The KeyKOS system for the Omron 88000 had a special range which allocated
the pages of the frame buffer.  Otherwise they checkpointed normally.  It
was quite impressive to see the screen quickly come back upon restart.  It
was so impressive that people tended not to notice that is was another
10-15 seconds before it reacted to user input.

>   [Reactions from the KeyKOS crowd? Is this necessary?  Is it okay
>   for the page fault handler to convert to DK(0) and yet special case
>   this?  One does not seem intrinsically more offensive than another
>   to me.]

Since the allocator is in a position to know what kind of page these pages
were, there is no information hiding principle that would make it
undesirable to tell the allocator directly.  The problem comes when you
want to virtualize these pages and use normal pages to replace them.  You
need an architecture which will allow you the rescind the normal page, but
give the expected error code.  You might be able to use single page kept
segments to achieve this.


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