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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc,comp.unix.bsd.netbsd.misc
Subject: Re: Curious about *BSD History
Date: Sat, 13 Apr 1996 12:55:48 -0700
Organization: Me
Lines: 26
Message-ID: <317006C4.77C0450E@lambert.org>
References: <4k1nue$lm8@orb.direct.ca> <3165791B.52BFA1D7@FreeBSD.org> <4kh916$1pa@cynic.portal.ca> <4kl863$rno@news.rhrz.uni-bonn.de> <1996Apr12.210743.28292@wavehh.hanse.de>
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:17356 comp.unix.bsd.netbsd.misc:3011
Martin Cracauer wrote:
] Some of NetBSD's developers want a bounce-buffer solution that is not
] specific to one spefic kind of device or one kind of machine. For
] example, the DEC Alpha machines have ISA bus, but to use ISA cards
] with DMA you *always* have to use bounce buffers, even with 16 MB of
] RAM.
I am more than passingly familiar with the 21066 Alpha boxes.
Why do you think DMA transfers *always* require bounce buffers?
How could you allocate such buffers from main memory, if no area
of main memory could be safely targeted in a DMA transfer?
Alpha needs bounce buffers for > 16M of memory -- but only in
that case.
Like Amiga needs bounce buffers for "device accessable" vs.
"device inaccessable" ("fast") RAM.
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.