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From: kjb@cs.vu.nl (Kees J Bot)
Subject: Re: Does Minix work on hard drives >1024 with LBA?
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Organization: Fac. Wiskunde & Informatica, VU, Amsterdam
Date: Thu, 23 Nov 1995 10:25:02 GMT
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jerijian@typhoon.seas.ucla.edu (Arthur D. Jerijian) writes:

>	I am going to take an operating systems class in about a
>month, and I need to know if Minix (1.5.x or greater) will work
>on my machine.  I have a Pentium 100 with a PCI bus and an Intel
>Triton chipset.  My hard drive is a Western Digital Caviar 1.2GB
>EIDE hard drive with my BIOS's LBA turned on.  I used Linux to
>format a 50MB Minix partition which Minix will reside on.  Will
>Minix work?

Minix before 1.7.0 does not know about IDE.  It uses the geometry
reported by the BIOS to access a disk.  So it will choke on a "fake"
EIDE geometry with more than 16 heads.

The Minix 1.7.0 AT disk driver ask the disk "are you IDE?".  If so
then it will ignore the BIOS settings.  Any (E)IDE drive should work.

<rambling>
Explanation of IDE buzzwords (software view):

IDE     The largest disk geometry the AT disk interface can handle is
	65536 cylinders, 16 heads, and 256 sectors.  The largest
	geometry that the BIOS interface can handle is 1024 x 255 x
	63.  So IDE disks with more than 1024 cylinders claim to have
	more heads and less cylinders than they really have, and
	translate incoming addresses to the internal geometry.

EIDE    Given the AT and BIOS geometry limits above, the maximum disk
	geometry is 1024 x 16 x 63 = 504 MB.  An EIDE BIOS tells the
	outside world that a large disk has a geometry with more heads,
	and translates addresses to a geometry with less heads and more
	cylinders to address the drive.

LBA	SCSI is good.  SCSI uses linear block addresses.  IDE must have
	linear block addresses.  The only good thing about it is that
	there is less translation overhead inside the drive, so it's a
	tiny bit faster.

Those BIOS setups are horribly confusing.  I wish they would just say
something like this:

   drive 0:	SAMSUNG PLS-30854A, 810 MB (1660176 sectors)

That's all we need to know.  (I'm not pushing Samsung, the nearby
Pentium happens to have one.)
</rambling>
--
	                        Kees J. Bot  (kjb@cs.vu.nl)
	              Systems Programmer, Vrije Universiteit Amsterdam
