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From: cau@cc.gatech.edu (Carlos Ugarte)
Message-Id: <199603250452.XAA24485@oscar.cc.gatech.edu>
Subject: Re: Crash advice needed APPENDIX B
To: rgrimes@GndRsh.aac.dev.com (Rodney W. Grimes)
Date: Sun, 24 Mar 1996 23:52:33 -0500 (EST)
Cc: uhclem@nemesis.lonestar.org, hackers@FreeBSD.ORG, current@FreeBSD.ORG
In-Reply-To: <199603230623.WAA26014@GndRsh.aac.dev.com> from "Rodney W. Grimes" at Mar 22, 96 10:23:23 pm
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> > 7.	It has been suggested that I remove the cache.  I'll just
> > 	mention that the cache and the board it is plugged-into were
> > 	both replaced earlier and there was no change in failure rate.
> > 	Further, this board/cache has no trouble with SCO UNIX,
> > 	Windows '95 and Windows NT which have all run on it previously

[snip]

> Because SCO Unix, Windows 95 and Windows NT are all gross in the way
> they handled bus master DMA disk controllers, they use a dedicated
> buffer area that is marked uncacheable just so they can run on the
> broken cache coherency motherboards.    Can you say totally defeat
> the purpose of bus master DMA buy having the processor bcopy data
> around...

Unfortunately, I've got one of these broken motherboards.  Is
there a way to make FreeBSD behave the same way?  That is, to
mark some memory block uncacheable (I guess this would be the
bounce buffers area)?  I realize this would be counterproductive
(decreased performance) in most cases, but in my case it might
help (I am able to use my DMA busmaster car at lower CPU
speeds, but I'd like to see the results of using a higher clock
value).

Carlos

-- 
Carlos A. Ugarte                                cau@cc.gatech.edu
Author of PageMage, a virtual desktop util for OS/2
http://www.cc.gatech.edu/people/home/cau/
Computer Science Senior at Georgia Tech