Date: Sat, 20 Jul 1996 22:18:26 +1000 From: Bruce Evans <bde@zeta.org.au> To: freebsd-scsi@FreeBSD.ORG, j@uriah.heep.sax.de Cc: jon@vcnet.com Subject: Re: 2940 and large drives Message-ID: <199607201218.WAA30953@godzilla.zeta.org.au>
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>> I turn OFF the option in the Adaptec for "extended BIOS for DOS-drives
>> larger than 1 gig" figuring maybe that option is ONLY for DOS drives. I
>It is only intended for stupid systems and always a good idea to turn
>it off. Infact, the BIOS is only used for booting in Linux or
on?
You want the option that gives a geometry of 63 sectors/track and 255
heads/cylinders as easily as possible, preferably be default, at least
for disks larger than 1GB.
>FreeBSD, and entirely ignored once the system comes up. The
>translation is only in effect while booting, since the BIOS doesn't
>provide a better abstraction of a disk than sectors, heads, and
>cylinders (without an unreasonably degraded number of bits available
>for each of them). Either SCSI as Unices provide the block number
>abstraction (also called LBA addressing), so no further translation
>happens other than adding an offset for the start of the slice and/or
>partition.
A geometry of 63/255 allows booting from anywhere on disks of size up
to about 8GB. If you don't use it, then booting from large disks may
be complicated (booting from cylinders >= 1024 is impossible).
Bruce
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