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From: guyd@austin.ibm.com (Guy Dawson)
Subject: Re: 386bsd with >16M
Originator: guyd@pal500.austin.ibm.com
Sender: news@austin.ibm.com (News id)
Message-ID: <C677BI.20Dz@austin.ibm.com>
Date: Wed, 28 Apr 1993 14:38:06 GMT
References: <g89r4222.735937533@kudu>
Organization: IBM Austin
Lines: 47
In article <g89r4222.735937533@kudu>, g89r4222@kudu.ru.ac.za (Geoff Rehmet) writes:
>
> Hi,
>
> This has probably been discussed before while I was not paying
> attention, anyhow....
>
> I am running a 386bsd system WITHOUT any SCSI devices, and thus
> assumed that it would be no problem to run the system with 32M of
> RAM. The system booted OK, until starting mountd, when it barfed
> with a VM fault.
The 16MB limit is NOT a SCSI problem! It's an ISA bus problem!
The ISA bus has 24 address lines so ANY card attempting DMA can only
do so with the first 16MB of memory.
The result is that ALL drives for cards doing DMA in a system with more than
16MB of memory need to deal with the problem.
>
> Is this due to problems with possibly trying to do DMA from the
> network card (WD)?
Almost certinally...
> Should I be able to run the system with 32M of RAM?
It depends on what the drivers support...
>
>
> Thanks,
> Geoff.
> --
> ============================csgr@alpha.ru.ac.za===============================
> Geoff Rehmet, Parallel Processing Group, |#define DISCLAIMER These are my
> Computer Science Department, | ramblings, not the
> Rhodes University, RSA. | University's
Guy
--
-- -----------------------------------------------------------------------------
Guy Dawson - Hoskyns Group Plc.
guyd@hoskyns.co.uk Tel Hoskyns UK - 71 251 2128
guyd@austin.ibm.com Tel IBM Austin USA - 512 838 3377