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From: bernhard@capucine.cica.fr (Christoph Bernhardt)
Newsgroups: comp.periphs.scsi,comp.os.linux.hardware,comp.unix.bsd.freebsd.misc,comp.os.linux.setup
Subject: Re: SCSI PCI host adapter
Date: 05 Sep 1995 11:14:12 +0200
Organization: Eurecom, Sophia Antipolis, FRANCE
Lines: 41
Sender: bernhard@capucine.cica.fr
Message-ID: <j0ld9dfq1wb.fsf@capucine.cica.fr>
References: <418r3m$9c6@trauma.rn.com> <1995Aug30.074902.1035@wavehh.hanse.de>
<42846g$2e9@trauma.rn.com> <42crke$hg@reason.cdrom.com>
<42ea9k$1sd@trauma.rn.com>
NNTP-Posting-Host: capucine.cica.fr
In-reply-to: larry@rn.com's message of 4 Sep 1995 03:36:20 -0400
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Xref: euryale.cc.adfa.oz.au comp.periphs.scsi:36640 comp.os.linux.hardware:14751 comp.unix.bsd.freebsd.misc:5435 comp.os.linux.setup:18941
>>>>> "Larry" == Larry Snyder <larry@rn.com> writes:
In article <42ea9k$1sd@trauma.rn.com> larry@rn.com (Larry Snyder) writes:
Larry> I'm stating for example, if I installed FreeBSD using the
Larry> 2940 controller, I should be able to remove the 2940 and
Larry> install the NCR controller and be able to boot the machine
Larry> and access the data on the hard driving using the NCR.
Larry> Is this not correct? In any case, the data written
Larry> (FreeBSD) with the 2940 not accessable using the NCR card
Larry> (after removing the 2940 and inserting the NCR card in the
Larry> PCI buss)
There might be a subtle problem with how the two controllers handle
the bios translation for your hard drives. You formatted and installed
your drive using the adaptec controller and its bios translation for
the drive geometry. If you start using the NCR now it must use the
same translation to boot from the disk. This might or might not be the
case. The NCR has an automatic translation scheme that maximizes the
capacity of the drive within the constraints of the bios
head,cylinder,sector limit. So the NCR might come up with another
translation than your adaptec, and yup your drive does not work
anymore. As far as I know the NCR is supposed to look into the
existing partition table to read the drive geometry and, if existing,
to use this translation. The problem now is that the NCR performs some
sanity checks on the information it finds and if the check fails it
uses its own automatic translation. Again as far as I know this sanity
check is a little insane by itself. So even with an existing partition
table (written by the adaptec) you might end up with the wrong
translation in the NCR.
Christoph
PS: If anybody needs more details ... I could maybe dig up the C'T'
article where I got my knowledge from ... in german ;-)
--
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Christoph BERNHARDT | "Every time I think I know where
Institut EURECOM | it's at, they move it."
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