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From: mw@theatre.pandora.sax.de (Martin Welk)
Subject: Re: Problem With Fujitsu SCSI Drive
Organization: Private Site, Member of Individual Network e. V.
Message-ID: <DH3H72.EoJ@theatre.pandora.sax.de>
References: <814658177.16718@kiss.demon.co.uk> <46mhpe$qok@trout.progroup.com>
Date: Fri, 27 Oct 1995 06:40:14 GMT
Lines: 46
In article <46mhpe$qok@trout.progroup.com>,
Craig Shaver <craig@progroup.com> wrote:
>Sounds like the original geometry after the low level format was
>correct. Do it again and go through the whole install. the dos
>fdisk may screw it up for you. It uses the bios, which is a spoof
>on the real geometry. Dos cannot handle greater than 1024 cylinders,
>so many controllers rearange the drive geometry to increase the
>number of heads and sectors and get the number of cylinders down
>to a 10 bit number or less. I have run into something similar on
>(I think ???) a quantum 500mb drive. The dos fdisk screwed up
>something and I cured the problem by doing a low level format.
SCSI host adapters see a disk drive as a number of 512k blocks.
The map the number of sectors to a logical (you may also call
it virtual) geometry to make the drive usable by DOS and other
int-13-BIOS-services-using operating systems.
You may use the original (hardware) geometry for FreeBSD but
only if you don't run other operating systems on the disk.
DOS will screw up with that. To be compatible to DOS
you have to use the BIOS geometry.
Adaptec SCSI host adapters always use a geometry with 32 sectors,
64 heads and a capacity-dependent amount of tracks (for my 990 meg
drive, this makes 32 * 64 * 991, for my 245 meg drive about
32 * 64 * 238, for my 520 meg drive it's 32 * 64 * 507, I think.)
To use the last bytes of a disk (the mapping causes loss of some
blocks at the end of the disk) you have to address it as a number
of blocks starting with zero and ending with the highest block
number on the disk.
Ah, and what we shouldn't forget: older Adaptec 1542B BIOSes (like
mine) cannot handle drivers over 1 gig. You need a BIOS update,
which is freely available on their ftp server and their BBS (at
least, here in Germany it is.)
Bye,
Martin
--
/| /| | /| / \ ,,You know, there's a lot of opportunities,
/ |/ | artin |/ |/ elk \ if you're knowing to take them,
\ you know, there's a lot of opportunities,
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Meissen, Germany, Europe \ make or break them!'' (Tennant/Lowe)