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From: Terry Lambert <terry@lambert.org>
Message-Id: <199603312029.NAA11754@phaeton.artisoft.com>
Subject: Re: fdisk and partition info
To: joerg_wunsch@uriah.heep.sax.de
Date: Sun, 31 Mar 1996 13:29:21 -0700 (MST)
Cc: freebsd-hackers@FreeBSD.org
In-Reply-To: <199603302241.XAA04940@uriah.heep.sax.de> from "J Wunsch" at Mar 30, 96 11:41:36 pm
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> > > I don't see any such assumption.  I have 3 SCSI controllers: U34F,
> > > BT445C and SC200.   I've only used the U34F with 64/32 geometry.
> > > The BT445C and the SC200 work with assorted drives in assorted
> > > translation modes giving 64/32, 128/32 and 255/63 geometries.
> > 
> > What happens if you turn of translation on the things?  (yes, I
> > know this is not a possibility for Adaptec).
> 
> I wonder how you wanna turn it off: the SCSI protocol does only know
> about locical block numbers, so if you wanna interface the drive with
> some int 0x13 C/H/S value, you always end up with some sort of
> translation.
> 
> If you speak directly in SCSI block numbers, nothing will be
> translated at any time.

Definitions for SCSI translation taking ZBR into account:

Untranslated:	H		= Real number of heads
		C		= Real number of cylinders
		S		= ? (some average)
		C * H * S	= Actual number of sectors, or less
		C/H/S is as reported by SCSI sense.
		Cylinder transitions do not take place at calculated
		boundries because of ZBR.  Calculation is possible
		using non-linear (table vs. step function) lookup
		based on SCSI II physical geometry reporting.

Translated:	H		= (H<=64)
		C		= (C<=1024)
		S		= (S<=256)
		C * H * S	= Actual number of sectors, or less
		C/H/S does not match SCSI sense.
		Cylinder transitions do not take place at calculated
		boundries because of ZBR.  Calculation is impossible.

Problem translation only occurs when a controller query and a BIOS
INT 13 AH=8 AL=<drive ID: 0x80, 0x81, ...) do not return the same
values.

Translation in the drive because of ZBR can be ignored.

Translation in the drive for sector sparing can be ignored (but should
not be for striping and RAID, because of spindle sync being thrown off
by the relocation.

					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.