*BSD News Article 36129


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From: Havard.Eidnes@runit.sintef.no (Havard Eidnes)
Newsgroups: comp.os.386bsd.questions
Subject: Re: SCSI and NetBSD PRoblems
Date: 24 Sep 1994 10:42:16 GMT
Organization: SINTEF RUNIT, Trondheim, Norway
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Distribution: inet
Message-ID: <360vq8$kdo@ugle.unit.no>
References: <357404$nb0@hermes.unt.edu> <MICHAELV.94Sep14135750@MindBender.HeadCandy.com> <357ka5$123@hermes.unt.edu> <MICHAELV.94Sep15000641@mindbender.headcandy.com>
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Originator: he@ravn.runit.sintef.no

In article <MICHAELV.94Sep15000641@mindbender.headcandy.com>,
Michael L. VanLoon <michaelv@MindBender.HeadCandy.com> wrote:
>
>NetBSD doesn't support more than 16MB of RAM with an *ISA*-bus SCSI
>controller.

Slight correction: NetBSD doesn't support more than 16MB of RAM with
a ISA-bus *DMA-based* SCSI controller.  For one, I don't think the 
AHA-152x controllers (can) do DMA.  On the other hand, from a performance 
perspective recommending AHA-152x probably isn't such a great idea,
and there are other reasons for not buying Adaptec cards (mentioned
here earlier).

The wd disk driver (for IDE drives) also does programmed IO and not DMA,
and I understand that's the reason this driver works just fine in a 
ISA-based system with more than 16MB RAM.  The same thing about
performance probably applies here as well, though...

- Havard