Geneve CPU Memory Upgrade

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Illustrated description

This can be found on Mainbyte's site:

Geneve 32K SRAM expansion

Original article by Tim Tesch

A few people have asked how to modify their Geneve with the extra 32K SRAM, to give them extra memory and let them use MDOS 2.50 and above. So... here we go...

Requirements:

  • Soldering iron, 15-20watt max.
  • Solder, use rosin core NOT organic core
  • 8" piece of wire-wrap wire.
  • (1) 32Kx8 SRAM (Hitachi 62256 compatible)

Disclaimer: If you are not comfortable modifying your equipment, DO NOT PERFORM THIS UPDATE! I will NOT replace blown gate-arrays or 9901s for free! Enough said.

Step 1

Carefully remove 32K chip from Geneve, noting the ORIENTATION. The square/half-circle should be facing the back of the card (joystick/mouse/video connectors.) If you are not sure, use a Sharpie or piece of tape to keep track of the position.

Use a small, wide-blade, flathead screwdriver. Apply gentle pressure to the TOP of the memory chip with your thumb, while gently "prying" between the memory and its socket. DO NOT PRY ONE SIDE COMPLETELY. Doing so will bend the pins on the opposite side. Pry the chip a bit at a time, switching from one side to the other until the chip is free.

This chip is located to the left of the battery, directly below the 12volt regulator. If you do not recognize this chip - STOP! Send in your card :)-

Step 2

Stack the new 32K chip on top of the existing memory.

Place the newchip on top of the old chip. The square/half-circles MUST lay "on top" of one another. BEND pin #20 enough so that it does not contact the pin underneath. You may do so using a small-blade screwdriver. Here is a visual representation:

 1 1 1 1 1 
 4 3 2 1 0 9 8 7 6 5 4 3 2 1    
+----------------------------+
|                            |
|       HM62256-10          (
|      (upside down)         |
+----------------------------+
 1 1 1 1 1 2 2 2 2 2 2 2 2 2 
 5 6 7 8 9 0 1 2 3 4 5 6 7 8 
           ^
           ^
           ^
* DO NOT SOLDER THIS PIN TO ITS NEIGHBOR BELOW *

Step 3

Insert stacked chips into socket. Chip should be inserted as shown above, half-moon to the right. Make sure pin #20 clears the EPROM so that you can solder the wire to it as shown in step #4.

Step 4

Solder wire to memory.

Strip and tin one end of the wire. Solder to pin #20, taking care not to short it with (a) any adjoining pins or (b) the EPROM directly below.

Take the wire and bring it to the underside of the board. You can go around the "top" or "bottom". DO NOT GO THROUGH THE HOLES NEAR THE EDGE CONNECTOR! While tempting, you run the risk of stripping wire and shorting something. worst-case, you short the wire with +16 volts! This would not be a good thing.

Step 5

Solder wire to underside of Geneve - GATE ARRAY. This step MUST be done carefully and exactly. If you make a mistake, you risk blowing out your gate array. This chip will cost you about $45.00 to replace.

Strip the wire, exposing no more than 1/8". We will solder the wire to the gate array as follows:

<<<- mouse/joystick/video<<<

            o o    Gate Array     o o   
            o o  (underside of    o o
            o o        board)     o o
            o o                   o o
            o o                   o o
            o o o o X o o o o o o o o 
              o o o o o o o o o o o 


"X" marks the spot. Carefully solder the wire to this pin.

Make sure that you do NOT short any of the three surrounding pins. In case you wish to count, it is the FIFTH pin from the left, TOP row.

Step 6

Test the geneve

Replace clamshell and put into your pEB/Case. Turn on the power and see what happens If all went well, you should boot without any problem. Once booted, type CHKDSK at any valid disk. You should see:

589824 bytes of total memory

Step 7

Pat yourself on the back - you've successfully modified your geneve! Go try MDOS 6.00.