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Date:      Fri, 10 Mar 2000 19:41:00 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        Jay Oliver <kythorn@scorched.com>
Cc:        freebsd-questions@FreeBSD.ORG, freebsd-hardware@FreeBSD.ORG
Subject:   Re: Having problems with a 40 gig IDE drive.
Message-ID:  <Pine.BSF.4.21.0003101923140.4112-100000@alphplex.bde.org>
In-Reply-To: <004301bf8a5d$c7068c70$2260e4d0@CHAOS>

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On Fri, 10 Mar 2000, Jay Oliver wrote:

> Having problems getting FreeBSD to play nice with a 40 gig IDE drive I
> picked up a while back.  Originally had problems with it under linux 2.2.13,
> but those were resolved as of 2.2.14.
> Currently using 3.4-STABLE

3.4 doesn't really support drives larger than 33.8GB.  Use LBA mode, and
don't enable panic dumps.

> wdc0: unit 1 (wd1): <Maxtor 94098U8>
> wd1: 39082MB (80041248 sectors), 79406 cyls, 16 heads, 63 S/T, 512 B/S
                                   ^^^^^

IDE drive hardware only supports 65536 cylinders.  If you see more than
that here, it means that the driver will screw up disk addresses.

> Trying to use the fdisk portion of /stand/sysinstall post install
> configuration informs me that the 'A geometry of 79406/16/63 for wd1 is
> incorrect, using a more likely geometry.  It switches to 4982/255/63.  No

This is probably OK.  Neither of these geometries is supported by IDE drive
hardware.  The driver ignores any changes here and keeps using the default
geometry (which doesn't work if it has too many cylinders).  The geometry
"used" for writing partition tables needs to be consistent and acceptable
to the BIOS.  xxx/255/63 is normal for drives larger than a few GB.

> matter what I try, I cannot get this to work properly.  I have heard there
> were problems with the driver in 3.x for larger drives in CHS mode, however
> this drive is in LBA mode, or so the BIOS informs me anyway.

This just means that the BIOS uses LBA mode in each i/o command that it
sends to the drive.  The wd driver has no idea which mode the BIOS uses.
It uses CHS mode unless it is condifured to use LBA mode.

Bruce



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