Addendum To The File Labeled 25MGUPGD.TXT 4 Megabyte Hardware Modification A Shareware File by Barry Orlando Dated: Jan. 15, 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 mega bit 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. The procedure described here has not been performed by me yet 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. Desolder and remove the remaining 16 256K chips (U46 through U61). 2. Using the Exacto knife, cut the following traces on the pc-board: a. Between U61's pin 1 and a 33 ohm resistor. Note: The other side of this resistor comes from U15's pin 63. b. Between U46's pins 2 and 14. Do the same for U47 through U61. c. Between the thru-hole between U46 and U47 and the thru-hole between U32 and U33. Note: This trace is on the top side of the pc-board. d. Between each of U47's thru U53's and U55's thru U61's pin 2 or 14 and the thru-hole behind it. These thru holes are the ones that you will find trace back U22, U23, U26, and U27. They are the same 1 ones that are wired to sockets pins 1 and 17 of the sockets installed by the 2.5 meg upgrade. 3. 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 all 16 will have their pin 18's flat and pointing straight out to the side. Also solder all sockets to the pc-board as was done before. 4. Wiring Wire the following connections on the top side of the board: a. Remove U32's top of pc-board wiring (i.e., from the 2.5 meg upgrade) and install new wire between U32's new socket's pins 1 and 17, U46's new socket's pins 1 and 17, and either pin 18 of U22 or pin 9 of U26. Solder the wire directly to the side of the chips pin or at a suitable trace point a thru-hole on the pc-board between U32 and U33. b. Remove U16's top of pc-board wiring (i.e., from the 2.5 meg upgrade) and install new wire between U16's new socket's pins 1 and 17, pins 1 and 17 of U54, and either pin 18 of U23 or pin 9 of U27. Solder this wire directly to the side of the chips pin or at a suitable trace point. c. Between each of the remaining new 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 were traces back to either pin 2 or pin 14 of U47 through U61 but still trace over toward U22, U23, U26, and U27. So that's 14 more wires altogether (i.e., each new RAM chip's pins 1 and 17 will be connected to the pins 1 and 17 of the chip directly in front of it. You may choose to rewire pins 1 and 17 of sockets installed by the 2.5 meg upgrade, however this is optional. Wire the following connections on the bottom side of the board (Note: all pin numbers here refer to the pin numbers on the pc-board, not the pin numbers of the new sockets or new ram chips): d. 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. e. Between all pin 2's of U46 through U61 and the thru-hole near R91 which had its trace cut to U30's pin 4. This thru-hole traces back on top of the pc-board under the bank of resistors and over to U15. f. Remove wire between U61's pin 1 and U30's pin 4, and rewire U30's pin 4 to U61's pin 4. Both U30's pin 4 and U61's pin 4 will now trace back to the cut trace side of resistor R76. g. Remove wire between U30's pin 1 and U61's pin 3, and rewire U30's pin 1 to U61's pin 1. 2 5. Inspect all solder joints with the magnifier for solder shorts and faulty connections. Verify that all connections were made correct. 6. Install the new 1 meg RAM chips into their new sockets. 7.That's it, unless I left something out? Remember this procedure has not been tested for accuracy! 8.Reassemble the computer and reconnect the monitor and power cord and power up. Wow...... 4 megs! Shareware Policy This file is provided to all registered users of the Shareware File 25MGUPGD.TXT ($15.00 registration fee required). Please do not make copies of this documentation and give it to others. Please feel free to send any comments or suggestions to me: Barry Orlando 1120 Deerfield Dr. Napa, Ca 94558 (707)257-2326 (evenings) Since this document is unproven in that it describes a procedure that has not been actually accomplished, all registered users will be sent free updates to this documentation as soon as it has been tried and updated by me or one of the registered users. 3