*BSD News Article 72057


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From: brian@awfulhak.demon.co.uk (Brian Somers)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Help!  BSD doesn't recognize new Memory
Date: 20 Jun 1996 04:48:48 +0100
Organization: Coverform Ltd.
Lines: 14
Message-ID: <4qahn0$7b@anorak.coverform.lan>
References: <4pnp56$m6@larry.rice.edu> <Dt53My.q9@info.elvisti.kiev.ua> <Pine.NEB.3.93.960617200228.499B-100000@tomqnx.tomqnx.com>
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Tom Torrance at home (tom@tomqnx.com) wrote:
: Another shot in the dark --> does your kernel have the double buffering
: support for DMA compiled into it? If not, it would not work properly with
: more than 16 Meg.  DMA hardware cannot address above 16 Meg.

DMA hardware can address above 16Meg.  An ISA (and some EISA) bus has only
got sixteen bits of address, therefore the memory address that is plonked
on the bus gets "wrapped" and shits all over something else.

There's nothing 16meg'ish about DMA'ing over a PCI bus for example.

--
Brian <brian@awfulhak.demon.co.uk>
Don't _EVER_ lose your sense of humour....