From: dnichols@d-and-d.com (DoN. Nichols)
Subject: Re: Help needed to bring life back to my old UNIX PC
Organization: D and D Data, Vienna VA
Date: Sun, 24 Jan 1993 05:53:12 GMT

In article <1jrjreINNc4o@kirov.intercon.no> aras@intercon.no (Arne Asplem) writes:
>I need some help to bring life back to my old UNIX PC. The 20 Meg.
>harddisk crashed totally some time ago, and obviously the computer hasn't 
>been used since. I need some information about which harddisks (controller
>type, size, etc.) are supported ? Preferably something larger that 20
>Meg. (in the range 60-100).

	Essentially, you can (with a totally stock machine) use any hard
drive that will physically fit (that is half-height for the 7300,
full-height for the 3B1), and that is MFM.  However, with a totally stock
machine there is some limitation on *how much* of it you can use.  There are
two limits.  One is that it will not use more than eight heads, even if the
drive has more.  The other is that it cannot use more than 1024 cylinders,
even if the drive has more.  There are fixes for each of these problems.

First, my suggestion for the best drive to put in a 7300, which is what I
presume you to have, since you are starting with a 20MB.  The best drive
which I have found and used is the Miniscribe 3085, which is a half-height
drive with seven heads (but greater than 1024 cylinders - don't worry, this
is the easier thing to fix.)

	To fix the cylinders limitation, you need to pull out the WD1010
hard disk controller chip (a 40-pin DIP in the cpu board), and replace it
with a WD2010.  This *may* necessitate applying the DRUN patch, which is
documented on the archives at OSU-CIS.  The simplest thing is to try it, and
if it works, you already have the DRUN patch applied.  If it has loads of
errors, you need the patch.  In that case, go back to the WD1010 chip and
format the drive to the maximum number of cylinders (1024) that it can use.
Then get the DRUN patch information, and the program 'cdraw' from the
OSU-CIS archives (or the ftp.uu.net ones).  Cdraw is necessary to display
the graphics in the DRUN patch instructions to help guide you in the
application of the patch.  Then apply the patch, and re-format the drive to
give you the whole thing.  (The 7300 and the two 3B1s that I have checked
have all had the patch applied.)

	You will have difficulty locating the WD2010 chip, since it is out
of production.  There is an Intel work-alike which you can get, but I don't
remember the number.  What I do to get a WD2010 chip is look at hamfests,
computer repair places, etc, for Western Digital hard disk controllers for
IBM PC and AT clones.  *Some* of these use the WD2010.  One I found had the
chip socketed, the others required unsoldering the chip.  Remember that in
this case the reverse philosophy to usual chip unsoldering applies.  You
don't give a damn about the board surviving, but you want the chip intact.
If you need hints as to how to do this, e-mail me and I'll try to type up a
guide.  If uncertain of your skills, practice on other chips on the board.
BTW - a bad or used controller card of this vintage shouldn't cost more than
$15.00, and may be as little as $5.00.  Even the $15.00 is less than the
list price for the chip, *if* they have the chip.

	The heads limitation is a greater problem.  For this, you need to
get the Icus-II kit, or the P5.1 PAL.  The P5.1 just allows you to go to 16
heads, while the ICUS-II allows you to ad a second drive (which *must* be
external, thanks to space limitations and power supply inadequacy.)  I put
*both* hard drives in an external case, reducing the load on my power
supply.  The ICUS-II kit is made by Gil Klopfer, and is not *that* much more
work that adding the P5.1 PAL.  Both require surgery on the CPU board.  If
you don't want to try this, and can't find someone else who can do it on
your behalf, you are stuck.

	Hmm ... looking at your return address, you may have trouble finding
the WD2010 with the way that I am suggesting.  I'm not sure *what* the
market for used PC-clone boards is over there.  I was talking about the
options given my own local experience.  Anyway, the ICUS-II kit does *not*
obviate the need for the WD2010 chip if you are going to use drives with
greater than 1024 cylinders.

	With both fixes in place, the largest MFM drive made is the Maxtor
2190, and its work-alike the Priam 219.  These drives will give you somewhat
less than 160MB of usable disk space, per drive, on the 3B1/7200.  Needless
to say, you need an external box with adequate power supply, and you will
have to do some interesting cable construction to make the mods here.

>My other problem is that I'm missing some of the operating system 
>floppies, specially the boot/install diskette ! Can someone help with this ?

	Here, at present, your best bet is to get one of the 3.51 foundation
sets available at the Chicago Warehouse full of 7300s, about which recent
postings have appeared in this newsgroup.  It was within the last week, If I
remember correctly.  If it has expired on your site, or if the distribution
has prevented it from reaching you, e-mail me, and I will dig up a copy.  I
*think* that the foundation sets are selling for $100.00 each.  (This does
*not* include the development set, which you have to find by haunting this
newsgroup till someone offers it, and pouncing quickly, since they seem to
be more scarce than the machines.

	Good Luck
		DoN.
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