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From: brian@sdcsvax.UCSD.EDU (Brian Kantor)
Newsgroups: comp.sys.att,comp.sys.ibm.pc
Subject: Re: Help needed with AT&T 6300 hard disk problem!!
Message-ID: <4335@sdcsvax.UCSD.EDU>
Date: Tue, 1-Dec-87 16:12:05 EST
Article-I.D.: sdcsvax.4335
Posted: Tue Dec  1 16:12:05 1987
Date-Received: Fri, 4-Dec-87 22:51:32 EST
References: <2225@killer.UUCP> <2306@homxc.UUCP> <1048@kodak.UUCP> <6913@sunybcs.UUCP>
Reply-To: brian@sdcsvax.UCSD.EDU (Brian Kantor)
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Organization: UCSD wombat breeding society
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Xref: mnetor comp.sys.att:1934 comp.sys.ibm.pc:10677

In article <6913@sunybcs.UUCP> ugweinst@joey.UUCP (Michael Weinstein) writes:
>
>	In reference to AT&T Hard drives, I was wondering if anyone
>	knew of a way to use a legit 86 Meg AT&T Hard Drive with an
>	IBM PC. I doubt if there is a way, but I have one available
>	to me, and if possible, I would like to utilize it. Any help
>	would be GREATLY appreciated.
>	ugweinst@sunybcs 
>	-----------------------------------------------------------


To use ANY hard drive with an IBM PC or PC/XT, you just have to set up
the tables that are used to describe the drive to the system.  This
varies from controller to controller in its exact details, but this
example may help you do it to yours.

In the DTC 5150BX controller, there is a table in the ROM contained on
the controller card that is accessable to the BIOS when the machine
boots.  There is also a switch.  The switch is set to point to the
proper table entry to use for each of the two possible drives on that
controller.  I assume that other XT compatable controllers work similarly.

In the ROM table there are entries for 4 items of importance that change
from drive to drive.  These are 1) the number of cylinders, 2) the
number of heads, 3) the cylinder upon which to reduce write current, and
4) the cylinder on which to change write precompensation.  There are
other things in there that you can change, but you probably won't have to.

If you know or can find out these for your drive, you can configure your
controller to accept the drive.  All you have to do is burn a new rom.
Since you can read the old rom without pulling it out of the board (it's
memory mapped into c800:0000 [I think that's the right address], you can
just move a copy of it with DEBUG, make the changes, save them on disk,
and then fire up your ROM burner.  After you've got the new rom,
disconnect your good disk, stick in the new rom and drive, and go for it.
Most controllers have an entry specifically reserved for use with
"custom" or nonstandard drives, so you can use that if you're not
already using it for your existing hard drive.

I've done this with several different drives - in fact, it's so easy,
that this is how I test surplus drives, since I have little other use
for an IBM PC, and it takes only a few minutes.

Enjoy.  Try not to break anything.

	Brian Kantor	UC San Diego

   "There is more harmony in films than in life."
	- Francois Truffaut