Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!helps!bigtex!james
From: james@bigtex.cactus.org (James Van Artsdalen)
Newsgroups: comp.unix.sysv386
Subject: Re: Why don't they use INT 13h throughout boot?
Message-ID: <49634@bigtex.cactus.org>
Date: 12 Nov 90 08:02:45 GMT
References: <35811@cup.portal.com> <49608@bigtex.cactus.org> <35858@cup.portal.com>
Reply-To: james@bigtex.cactus.org (James Van Artsdalen)
Organization: Institute of Applied Cosmology, Austin TX
Lines: 17

In <35858@cup.portal.com>, ts@cup.portal.com (Tim W Smith) wrote:

> Finding out what mapping was being used by INT 13h shouldn't be
> a problem.  The boot code would ask the INT 13h code for this
> and pass it to the kernel.

The BIOS doesn't have a call to return the mapping, just the apparent
geometry.  While this is going to be almost always sufficient to
deduce the mapping, it's not guaranteed.  For example, right now
bigtex is running a configuration where the apparent geometry is one
sector per track greater than what's actually used, and BIOS claimed
cylinders half reality & the sectors per track twice (after the
addition).  It's a long story as to how this came to be, and I've
never bothered to fix it.
-- 
James R. Van Artsdalen          james@bigtex.cactus.org   "Live Free or Die"
Dell Computer Co    9505 Arboretum Blvd Austin TX 78759         512-338-8789