*BSD News Article 35975


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Newsgroups: comp.os.386bsd.bugs
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From: paul@pp2.smc.south.telia.se (Paul Pries)
Subject: Re: aha0: DMA beyond end of ISA
Message-ID: <1994Sep20.191523.26387@palantir.p.tvt.se>
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Date: Tue, 20 Sep 1994 19:15:23 GMT
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kstailey@leidecker.std.com (Kenneth Stailey) writes:
: I have a 486DX-2/66 with NetBSD 1.0_BETA and a middle-aged AHA 1542A
: controller (it seems ok with AHA_NSEG defined as 17).
: 
: When I raise the core memory (RAM) from 16MB to 20MB I get:
: 
: aha0: DMA beyond end of ISA
: 
: error messages.
: 
: Why does this happen? Is there anything that will fix this?
: 
: Ken

It's quite simple. The ISA bus can't handle more than 16MB of
memory. That is, if there are no bouncebuffers implemented.

There is a soloution, but I'm not sure i dare to mention it, 
as it's not so popular in all the different *BSD cams...
I'll just wisper it ;-) :
psst, use FreeBSD, it has bouncebuffer support.

Flames > /dev/jesus  ;-)

Cheers,
		Paul.

--
Paul Pries
paul@smc.south.telia.se