🚀 go-pugleaf

> 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

In article <7739@lanl.ARPA>, myxm@lanl.ARPA (Mike Mitchell) writes:
> > 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). .........
> Hope this helps. 
> 
> Mike Mitchell
> myxm@lanl.arpa
I hooked two 10M drives to the XEBEC  controller in an ITT XTRA.  The cable 
twisting was avoided by setting the second hard disk to respond as drive 1 - 
not drive 0.   I believe the twist in the cable is used so both drives can
be configured as drive 0.

Ray Galvin

In article <332@mit-amt.MIT.EDU> mob@mit-amt.MIT.EDU (Mario O. Bourgoin) writes:
>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.
>I want to add one from an XT that is unused. I have looked at the XT
>reference manual and the hardware and I can't see a way of controlling
>an extra disk using it.

Look again.  The standard IBM controller handles two 10 MB disks.  They
even provide the cabling; all you have to do is take the second drive and
plug it in.  There isn't physically room in an XT for two hard drives and
a floppy, though, so you need an expansion chassis, which is expensive, or
else some half-height drives.

I have personally plugged two drives into the controller many times (in an
expansion box, because we had them) and it works just fine.

John Levine, ima!johnl
-- 
John R. Levine, Javelin Software Corp., Cambridge MA +1 617 494 1400
{ ihnp4 | decvax | cbosgd | harvard | yale }!ima!johnl, Levine@YALE.EDU
The opinions expressed herein are solely those of a 12-year-old hacker
who has broken into my account and not those of any person or organization.

In article <218@ima.UUCP> johnl@ima.UUCP (John R. Levine) writes:
>Look again.  The standard IBM controller handles two 10 MB disks.

In fact, the controller in newer IBM XTs will handle any combination of two
drives out of four drive types.  Three of these four types are 20 meg
drives.  I am writing this article on an XT with 2 Seagate ST-225 (20 meg)
drives hooked to its IBM controller.  To tell if your controller is of this
newer type, look for a four position dip switch near the mounting bracket.
Older controllers have solder pads and silk screen markings where this switch
could be mounted, but no switch.  Older controllers will also handle any two
out of four drive types (if you add the switch), but the types are different.
I suspect (but do not know) that the only difference between the older and
newer XT controller is the switch, and a different ROM (the ROM contains the
fixed disk bios including the disk type table).

This information is taken from the "IBM Technical Reference, Options and
Adapters."  The relevent sections are "IBM Fixed Disk Adapter (#6361503)"
(for the older XT controller), and "IBM PC 20MB Fixed Disk Drive Adapter
(#6139790)" (for the newer controller).

Write me if you need to know what drive types are supported, or what the
switch settings are for a particular drive type.
-- 
Dave Shanks             ..!tektronix!tessi!atelabs!cds
AT&E Laboratories
1400 NW Compton  Suite 300
Beaverton, OR  97006
(503) 690-2000

> 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.
> I want to add one from an XT that is unused. I have  looked  at the XT
> reference manual and the hardware and I can't see a way of controlling
> an extra disk using  it.  I also  can't   see  a  way  of  having  two
> controller cards in the XT without contention between them.
> 
> Can someone suggest either a way of controlling an extra disk with the
> present controller  or  adding in a   second controller or  getting  a
> different controller? Or anything else?
> 
> --Mario O. Bourgoin

I haven't done this my self, but I know IDEA is able to do this with
their external hard disks.

Would you please post when you find out though??

Thanks and Good Luck,

Bill