Addendum To The File Labeled 25MGUPGD.TXT

                        4 Megabyte Hardware Modification


      
     A Shareware File by Barry Orlando     Dated: December 28, 1989 
      
       
      
     Introduction 

      
      
     This text file provides a procedure which details further modification
     of the 2.5 megabyte 1040ST computer to a full 4 megabytes. This
     procedure assumes that you have already made the modifications
     described in the file called 25MGUPGD.TXT and replaced 16 256K dynamic
     RAM chips with 16 one megabit dynamic RAM chips. The 4 meg modification
     simply replaces the remaining 16 256K dynamic RAM chips with another 16
     one megabit dynamic RAM chips.  Reinstallation of the ST's metal RF
     shield cover will still not be impaired.  Also since the 1 megabit
     DRAMs use CMOS technology, they use only one fourth the power for the
     same memory capacity, thus the built-in power supply of the 1040ST will
     not be affected.



     Disclaimer of Liability 
      

      
     I make no claim that this modification will work for you. This
     procedure has not been verified by someone other that myself, so I
     can't claim any accuracy to its content or system performance. 
     Performing this modification will be done at your own risk and may void
     the warranty on your computer.



     Procedure 



     1. Remove all of the 1 meg chips from their sockets.

     2. On the top side of the pc-board, remove all wires previously
     installed by the 2.5 meg modification. These are the ones attached to
     pin's 1 and 17 of the chip sockets and to the pc-board.

     3. On the bottom side of the pc-board, remove the wire connecting pin 1
     of U61 to pin 4 of U30; then remove the wire which connects pin 3 of

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     U61 to pin 1 of U30.

     4. Desolder and remove the remaining 16 256K chips (U46 through U61). 
      
     5. Using the Exacto knife, cut the following traces on the bottom side
     of the pc-board: 
      
          a. Between U61's pin 4 and the thru-hole between resistors R91 and
          R94.
          b. Between U46's pin 14 and the thru-hole between U46 and U47.
          c. Between U61's pin 3 and U60's pin 3. 
          d. Between U46's pins 2 and 14. Do the same for U47 through U61.

     6. Using the Exacto knife, cut the following traces on the top side of
     the pc-board:

          a. Between U46's pin 14 and U22's pin 3.
          b. Between U47's pin 14 and the thru-hole between U22 and U26.
          c. Between pin 2's of U48 thru U61 and the thru-hole behind each
          chip.

     7. Preparing New Sockets and Soldering Them In Place 
      
          a. Prepare sockets and "Socket Wrap-ID" plastic markers as were
          done for the 2.5 meg upgrade except that all but 3 will have their
          pin 18's flat and pointing straight out to the side. U46, U47 and
          U60 will require the sockets with their pin 18's bent back and
          down. Solder all the sockets in place.

     8. Wiring 
      
          Wire the following connections on the top side of the pc-board:  
      
          a. Between U32's socket's pins 1 and 17, U46's new socket's pins 1
          and 17, and pin 3 of U22. Solder this wire directly to the side of
          pin 3 of U22. 
          b. Between U16's new socket's pins 1 and 17, pins 1 and 17 of U54,
          and pin 18 of U27.  Solder this wire to the thru-hole next to pin
          18. Note: This thru-hole traces to pin 18 on the bottom side of
          the pc-board. 
          c. Between each of the remaining socket's pin 1 and 17 and a
          thru-hole in back of each new chip socket (i.e., U47 through U53
          and U55 through U61). These thru-holes are the ones that the trace
          was cut where they traced back to either pin 2 or pin 14 of U47
          through U61 but still trace over toward U22, U23, U26, and U27 and
          are the same ones previously used by the 2.5 meg modification. So
          that's 14 more wires altogether (i.e., each RAM chip's pins 1 and
          17 will be connected to the pins 1 and 17 of the chip directly in
          front of it.  
      
          Wire the following connections on the bottom side of the pc-board:
          (Note: all pin numbers here refer to the pin numbers on the

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          pc-board, not the pin numbers of the new sockets or new ram chips)

          d. Between pins 1 and 3 of U61.
          e. Between pin 1 of U30 and pin 3 of U61.
          f. Between all pin 14's of U46 through U61 and the 33 ohm resistor
          installed by the 2.5 meg upgrade. This connection is made on the
          same side of this 33 ohm resistor which is wired to pin 14 of U30.
          g. Between all pin 2's of U46 through U61 and the thru-hole near
          resistor R91 which had its trace cut to U61's pin 4.
          h. Between U61's pin 4 and resistor R76 (on the same side of the
          resistor as is wired to pin 4 of U30). 
      
     9. Inspect all solder joints with the magnifier for solder shorts and
     faulty connections. Verify that all connections were made correct. 
       
     10. Install the new 1 meg RAM chips into the front bank and reinstall
     the removed 1 meg RAM chips into the rear bank sockets. 
      
     11. Reassemble the computer and reconnect the monitor and power cord
     and power up.  Wow...... 4 megs! 

     12. Run the Dynamic RAM checker program named MEMTESTR.TOS to verify
     proper operation of the new chips (Bank 0).



     Shareware Policy 
      

      
     This file is provided as a part of the Shareware File 25MGUPGD.TXT
     ($15.00 registration fee required). Please feel free to send written
     comments or suggestions to:

      
                    Barry Orlando 
                    1120 Deerfield Dr. 
                    Napa, Ca  94558















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