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From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
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Subject: Re: ASUS ncr scsi controller question
To: heric@aug.com (Eric Hinson)
Date: Wed, 3 Apr 1996 14:39:25 -0800 (PST)
Cc: freebsd-hardware@freebsd.org
In-Reply-To: <199603300817.DAA14363@rocoto.aug.com> from Eric Hinson at "Mar 30, 96 03:17:16 am"
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> Hi,
> 
> I set up a drive with FreeBSD on an Adaptec 1542cf (on another system) and 
> would like to put the drive in a system with the NCR PCI-SC200.  I have 
> done this before successfully with no difficulty.
> 
> However, when I tried it with this new system, it works fine with
> an Adaptec 1542cf (even with 32 megs of ram), but gives me a
> 'missing operating system' message when I try to boot the same drive
> with the NCR based controller.
> 
> I encountered this same error with the adaptec before I turned off
> the > 1gig translation option in the Adaptec 1542cf BIOS.  After that, it 
> came up without incident.
> 
> I have moved drives from the Adaptec 1542cf based systems to the NCR PCI 
> based systems in the past without problems.
> 
> Any help you can provide would be greatly appreciated.  Thanks.

The problem you are experincing is due to disk drive geometry translation,
for disks < 1G byte the 1542 and the NCR use a 64 head/32 sector translation,
for drives > 1G the 1542 uses either 64/32 or 255/63 under your control, the
NCR does some really strange things above 1G and you have no control over
what it picks.

You did not have problems in the past because you moved drives <1G around
or just plain outright got lucky, OR you installed FreeBSD using the
_whole_ disk offset by 0 sectors (which I do manually so that I can move
disks around at will).


-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD