From: EBRALPH AT AUGSBURG DOT BAYNET DOT DE (Eduard Ralph)
Newsgroups: comp.os.msdos.djgpp
Subject: DPMI and Page swapping
Date: Tue, 22 Apr 1997 17:51:32 GMT
Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany)
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Message-ID: <5jitme$s6o$1@sparcserver.lrz-muenchen.de>
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To: djgpp AT delorie DOT com
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Hi,

this is actually an answer from a different thread (Growing Pains with
DJGPP) which I had started, but I felt this belonged to it's own
thread. This gives me a chance to show off my knowledge instead of my
short comings.

When you try to access a page of memory (beign 4k big) which is
currently swapped to disk, the processor generates an exception. From
there the handler takes over. It chooses a page which was accessed the
least, though it can choose any one, swaps that to disk and then loads
the page from disk. It then proceeds to change the GDT or IDT what
ever to correct the info and then calls up the instruction which
caused this fault. Generally it work fine and the software continues
as if it had never been interrupted.
The DPMI Server, which takes over this job, must know which are
swapped out and which are not, because a flag in the Table tells him
of the status.

I think that should be a correct and accurate description without
going into great details...

                 Eddie