*BSD News Article 21727


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Newsgroups: comp.os.386bsd.questions
Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!decwrl!csus.edu!netcom.com!netcomsv!resonex!michael
From: michael@resonex.com (Michael Bryan)
Subject: Problems with bus masters, ISA, >16MB memory
Message-ID: <1993Oct1.084404.15832@resonex.com>
Organization: Resonex Inc., Fremont CA
References: <1993Sep29.182618.11087@news.csuohio.edu> <1993Sep29.155751.2394@resonex.com> <CE5tu9.Eo5@veda.is>
Date: Fri, 1 Oct 1993 08:44:04 GMT
Lines: 19

In article <CE5tu9.Eo5@veda.is> adam@veda.is (Adam David) writes:
>Bounce buffers are not yet implemented in the SCSI system, and there may be
>other device drivers using busmaster DMA which have a similar problem. The
>ISA bus cards cannot address higher than the first 16MB, because there are
>not enough address lines. This is not a problem with EISA cards on an EISA
>bus, but continues to be a problem if ISA cards (or EISA cards configured
>for ISA compatibility) are used in an EISA system. Bounce buffers are
>implemented in the kernel for generic ISA bus access, but only the floppy
>driver is using this feature so far.

Is there any anticipation as to when the SCSI drivers (especially for the
disks) will be using the bounce buffers?  It's rather annoying to have to
yank 4MB of perfectly good memory from my system...

-- 
Michael Bryan          michael@resonex.com         +1 510 249 9600   Ext 325
Resonex, Inc.                    ____                              ____
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