From: "Charles Sandmann" <sandmann AT clio DOT rice DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Disabling cache?
Date: Tue,  8 Jul 1997 23:42:27
Organization: Aspen Technology, Inc.
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> I need to be able to turn the cache off for a specific memory area.

Calling the dpmi 0x800 call to map physical memory is supposed to turn off
caching for that area of memory (at least that was the plan...) as is
seen in the physical_map procedure in paging.c of CWSDPMI.  That's no
guarantee it works - it had no testing on devices needing caching 
disabled.  If it's broke and someone has a patch I'll try and fix it.
There are also some hacks floating around to modify the page tables 
from the 32-bit code - but the page cache might need to be reloaded.
It also might be a 386/486/P5 behavior difference.  I don't know.