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From: stuart@BMS-AT.UUCP (Stuart D. Gathman)
Newsgroups: net.micro.pc
Subject: Re: 40 Meg hard drive in pc/AT, HELP!
Message-ID: <239@BMS-AT.UUCP>
Date: Sat, 4-Oct-86 02:19:04 EDT
Article-I.D.: BMS-AT.239
Posted: Sat Oct  4 02:19:04 1986
Date-Received: Sun, 5-Oct-86 13:35:41 EDT
References: <260@psueea.UUCP>
Distribution: na
Organization: Business Management Systems, Inc., Fairfax, VA
Lines: 37
Summary: Brand X disks on PC-AT Use a ROM burner

In article <260@psueea.UUCP>, waldref@psueea.UUCP (Greg Waldref) writes:

> I am trying to install a Seagate st-251 40 meg drive in my AT

We have found the simplest method of installing Brand-X disks in PC's
is to use a ROM burner to copy the BIOS ROMS (from the controller for XT,
from the motherboard for AT) to your PC, patch the drive table and burn
new EPROMS.  

	I attempted the software solution initially, but finally
gave up as I lost count of how many places the ROM was accessed directly
instead of using the vector.  (How do you get the vector there before
DOS boots?  That's a good question: you have to modify the boot sector
to put it there for you.  Unfortunately, the rest of the boot sequence
has to be tweaked as well since that vector is not used consistently
until you are up and running.  I was able to make it work by booting off
a diskette and having a small memory resident program supply the hard
disk table.  This is hardly worth it.)  Modifying the ROM also works
for SCO Xenix (but not Microsoft, ie. IBM, Xenix.  You have to patch
several different programs: /boot, /xenix, /etc/fdisk, /etc/badtrack and
maybe some others.  How do you patch these before you install Xenix on
your new disk?  Ahhh, good question!  You pretend you are a smaller
supported disk; install; make the patch; reinstall.)

* * * G R I P E * * *

	Both ROM and boot programs are the absolutely wrong place to
put disk size information.  Any intelligent DOS (or Unix port) would
put disk size info on the home block of the disk (the boot sector) 
where it can always be read.  I can only think of snivelling marketing
reasons why Microsoft did things the way they did.  (You should have
bought True Blue.)  Actually, the info is already there provided you
don't have to worry about reduced write current and stuff!  The number
of tracks/cylinder and sectors/track can be deduced from the partition
table since partitions are required to reside on cylinder boundaries.
-- 
Stuart D. Gathman	<..!seismo!{vrdxhq|dgis}!BMS-AT!stuart>