         DISK DRIVE ADDITIONS FOR MORROW MICRODECISION 2

I  recently  added  two  additional  disk  drives  to  my  Morrow 
Microdecision 2 computer.   These notes describe the method used.  
While  these  instructions  worked  on my  computer,  I  make  no 
guarantee that they will work for your system.   Please be  aware 
that a mistake might void your warranty.


THE COMPUTER:

Morrow  has a number of different configurations in use in the MD 
series.   The system described here has Shugart SA200 disk drives 
and  a Rev.  1.1 motherboard.   This configuration has  2  serial 
ports,  no parallel port,  and an expansion disk connector at the 
rear of the computer.

                     Fig. 1:  MD2 REAR VIEW
 +-------------------------------------------------------------+
 | +---+                                                       |
 | | o |                                                       |
 | | n |                 This is it!                           |
 | +---+                      |                                |
 | +---+                      V                                |
 | | A |                 34         2                          |
 | | / |                 +----------+ +---------+ +----------+ |
 | | C |                 | DRIVE EXP| | P/M PORT| | TERMINAL | |
 +-------------------------------------------------------------+
 
Note the numbers above the drive expansion connector in Figure 1.  
They refer to the pins on the edge connector.

 
SOFTWARE:

Before you make any hardware changes,  make the needed changes to 
your  software.  (While you know everything still works!)  You'll 
have  to  set  up your CP/M to recognize  the  third  and  fourth 
drives.

To  do so,  place your CP/M distribution disk in drive A and boot 
the system.   Follow the prompts.  When it asks for the number of 
drives,  type '4'.   When you get to the main menu,  type ESC  to 
exit.  Place your CP/M distribution disk in a safe  place.

Boot  your new CP/M working disk.   You should be able to  access 
Drives A and B as before.   If this works, try accessing drive E.  
This  should  act as a virtual drive.   (You'll be  requested  to 
remove the disk from Drive A,  and insert the disk for Drive E .)  
Finally,  try accessing Drive C and Drive D.  For either of these 
drives,  you  should  receive an error message  inviting  you  to 
abort,  retry,  or  ignore  the error.   If you get  the  correct 
responses  from  the software,  you can then use SYSGEN  to  move 
copies  of the system to other disks.   Make sure that you have 4 
formatted disks on hand for testing.
.cp 5
HARDWARE:


To  add  the two drives,  you will need two Shugart SA200  drives 
(with  manual),  a dual horizontal disk drive cabinet with  power 
supply,  a 34 conductor cable with edge connectors, wire, solder, 
and hand tools.

Begin  with  the cable to connect the drives  to  the  computer's 
expansion drive connector.   You can buy it, or make it yourself.  
If  you make one,  you will need a length of 34 connector  ribbon 
cable  and  three matching edge connectors.   Assemble the  cable 
with  one  connector at one end,  and the  other  two  connectors 
spaced  about a foot apart at the other end.   If the  connectors 
are  the slip-on style,  be sure to install the connector  marked 
'C'  before  installing  the  other  connectors.    (Considerable 
pressure  may be needed to insure good contact between the  cable 
and the connectors.  A rubber mallet or vise may be useful.) 



                      Fig. 2: CABLE LAYOUT

 +-+ 2                                        2 +-+        2 +-+
 |E|============================================| |==========| |
 |X|============================================|C|==========|D|
 |P|============================================| |==========| |
 | |============================================| |==========| |
 +-+ 34                                      34 +-+       34 +-+


Next  prepare  the  drives.   Referring to  Fig.  3,  locate  the 
terminating resistor pack (T in Fig.  3) and remove  it.   Locate 
the Disk Select jumper and place the jumper at DS1.  This will be 
Drive C.

Preparing Drive D is a bit more complicated.  Some soldering will 
be  required,   so  plug  in  your  soldering  iron.   Leave  the 
terminating resistor pack in place.   Place a jumper at DS2.  Now 
refer to Fig.  3 and locate edge connector J2.   The pins on this 
connector  are odd numbered on the bottom,  and even numbered  on 
the  top.   Viewed from the front of the drive,  pin 2 is on  the 
right, and pin 34 is on the left.  Carefully solder a small piece 
of wire from pin 4 to pin 12.  It is important to solder the wire 
on  the  drive side of the pins,  so that the edge connector  can 
still  slide  over the pins.   This jumper connects +5VDC to  the 
Drive Select 2 input.   (Some documentation from Morrow indicates 
that pin 2 and pin 12 should be connected,  but that did not work 
in this case.) 


.CP5
             Fig. 3: PARTIAL TOP REAR VIEW OF SA200

                             J2                 J1
                      +--------------- --+   +------+
                      |34               2|   |      |
                +-----+                  +---+      |
                |        T +-----+  DS 1234         |
                |          +-----+     ::::         |
                |                                   |
                +-----------------+                 |


Next install the drives in the cabinet.   The Shugart SA200's are 
2/3  height drives that are to be installed  horizontally.   They 
may  be  mounted side - by - side,  as in the  MD2,  or  stacked.  
Important:   Install the drives horizontally,  with  the  printed 
circuit  boards  on the top.   If the printed circuit boards  are 
mounted underneath, the drives may be damaged.

Connect  the power supply to J1 of each drive,  and  perform  the 
initial checks listed in the SA200 manual.   Power up the  drives 
for the blue smoke test.  

If the drives are functioning properly at this point, install the 
cable  from the computer to the drives.   Take care that pin 2 on 
the computer is connected to pin 2 on the drives! 

Power up the entire system, and if it passes the blue smoke test, 
try  Drive  A  and  Drive B to make sure  that  they  still  work 
correctly.   Then try Drive C and Drive D.  You should be able to 
read  the directory for all 4 disks.   If things are still  going 
well, try to format the disks in Drive C and Drive D.  Use PIP to 
transfer files from A and B to C and D.   If that is  successful, 
check  to  insure that disks written on C and D can be read on  A 
and B.

With  care,  you now have a functioning four drive MD2.   If  you 
have  problems,  review  the entire  procedure.   Pay  particular 
attention to the disk connector cable;  it is the "weak link"  in 
the setup.



25-Nov-83

Stan Young
POB 8
Lilburn, GA 30247



Note: MicroDecision (R) is a product of Morrow Designs, Inc.
CP/M 2.2 (R) is an operating system developed by  Digital  Research, 
Inc.
ecision (R) is a produ