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From: myxm@lanl.ARPA (Mike Mitchell)
Newsgroups: net.micro.pc,net.micro
Subject: Re: XT controller for two hard disks.
Message-ID: <7739@lanl.ARPA>
Date: Sun, 21-Sep-86 14:41:12 EDT
Article-I.D.: lanl.7739
Posted: Sun Sep 21 14:41:12 1986
Date-Received: Sun, 21-Sep-86 18:50:04 EDT
References: <332@mit-amt.MIT.EDU>
Organization: Los Alamos National Laboratory
Lines: 29
Xref: mnetor net.micro.pc:6591 net.micro:6093

> I  need to control  two 10 Megabyte  hard disks  from  one  XT. The XT
> already controls one 10M hard disk  using the original IBM controller.

The IBM controllers that I have seen were made by XEBEC. These controllers
have the capability of running two hard disks. You can tell if your controller
will do this by looking at the place where the cables connect to it. You
should see three rows of staking pins. One should be 34 connecters and the
other two should be 20. If your controller is set up like this then all you
will need are the cables to hook up the drives. The 20 position cables have
nothing special to them. They run straight through. The 34 position cable has
a twist in it going to drive D (similar to the way the floppy cable has a
twist in it going to Drive A). The positions involved in the twist are:

 34               26|16  18  20  22  24|14          2          CABLE POSITION D
 34               26|  17  19  21  23  |14           1
                    |                  |
                    |                  |
                    \                  \
                      \                  \  
                           1/2 twist
                      /                  /
                    /                  /
 34               26|24  22  20  18  16|           2
 34               26   23  21  19  17               1         CABLE POSITION C

Hope this helps. 

Mike Mitchell
myxm@lanl.arpa