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From: jimr@applix.com (Jim Rouleau [ext 256])
Newsgroups: comp.sys.ibm.pc.hardware
Subject: 2 hard drives in 1 machine...HOW?
Message-ID: <1122@applix.com>
Date: 13 Feb 91 14:30:12 GMT
Organization: APPLiX Inc., Westboro, MA
Lines: 43


OK, here we go...  I am trying to install 2 hard drives in my AT.  I
haven't seen much info on the subject and I've asked around to no avail.
(The drives are a Micropolis 1325 and a Miniscribe 3425). I've lots of
questions, bear with me.
     The controller cable I'm using has the card connector, some straight
cable, connector '1', a twisted section, and finally connector '2'.

   X----------X---------X
   X----------X--\-/----X   not perfect, but you get the idea.
   X----------X---|-----X
   X----------X--/-\----X
             '1'       '2'

   Anyway, each drive will boot the machine if I connect it to
connector '1'.  What I would really like is to boot the machine with
the Micropolis and have the Miniscribe be drive 2. (but I'll take
the other way If I could even get that!).  I've tried different combos
with no luck.  I have configured the CMOS, so that's no problem.
I've also tried just booting the machine with either drive attached
to connector '2' and changing the select jumpers, but haven't been
able to boot the machine by doing this. I assume that I have the
jumpers set to drive select 1 when I am able to boot them
separately.

   What makes a drive first or second and how does the machine
distinguish them?  Is is just the data cable or does the controller
cable play too? (Does anyone know 'why the twist'? I,ve heard
"hard drive cables are different than floppy cables", but isn't 
the twist the only difference?) What about the terminating resistors?
Do I want the first physical drive on connector '1' or '2'?

   Another thing, what about the partitions?  Right now I've got a
bootable partition on each drive.  Will DOS be nice and allow me
to change the logical drive of the second physical drive so that
if the last logical drive of the Micropolis if E> and I cd to
F> then I will be accessing the Miniscribe? Or do I have to change
something first, while I can still access each drive as the first?

  As you can see, I have got a lot of bits and pieces, but haven't
managed to piece them together coherently enough to form the picture.
I might be the only one who doesn't understand this, but if there's
enough interest I'll post a summary.