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Date:      Mon, 1 May 1995 22:49:45 -0400 (EDT)
From:      Bao Chau Ha <>
To:        Terry Lambert <>
Subject:   Re: 950412-SNAP Installation with ESDI (WD1007V) System
Message-ID:  <>
In-Reply-To: <>

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On Mon, 1 May 1995, Terry Lambert wrote:

> As long as this is done in hardware rather than in BIOS, this type
> of remapping will be invisible.  I believe that at least some of
> the bad sectoring is handled by BIOS.
> I make this claim because the translated geometry you indicate is
> 636/16/63.  This implies that the 0-35 number you gave for the
> 1222/15/35 should really have been 0-63.
The translation is done in hardware by the firmware.  The mapping
is linearly from 1-35 sectors/track to 1-63 sectors/track.  Sector 
0 is always invisible.  The controller firmware ignores the spare 
sectors during the translation.  

The 63 sectors/track mapping was very popular few years back and 
used by ESDI and RLL controllers to overcome the 1024 cylinder 
limit of INT 13, since these drives tended to have 1224 or more 
> If you want to continue to work on loading the ESDI, let me know, and
> I'll give whatever assistance I can.
Thanks for the assistance.  I found out that the BSD partition (slice)
does not have to be within 1024 cylinder for boot up, just the root
partition.  So I change my geometry to 1222 cyl. x 15 hd. x 35 spt,
and it seems to work.  Still not sure why the 63 spt geometry is 
causing problems.  I have used the same drive using the 63 spt
translation with DOS, OS/2, Linux, and an ancient System V Rel. 3.0
(ESIX variant) a long time ago.  


Bao Chau Ha (
Nuclear chemical engineer by day, Linux hacker by night and weekends.

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