After recently managing to purchase a Zip GSX, I wanted to explore the possibility of modding the card to perform at higher speed. I came across a number of old text articles in the FAQ and also a hypercard stack that outlined the procedure. I mostly used the hypercard stack as a reference for performing my mod, except instead of using a .6" to .3" adapter, I chose to carefully cut away the center of the original IC socket and solder in some machined pin sockets.
Here are the steps I used to modify my Zip GSX to get it running stably at 12.5MHz:
| Remove all SRAM chips. On the 1st TAG socket, very carefully cut away the plastic strips from the IC socket (exposing the solder points beneath). |
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| Perform the same operation for the 2nd TAG socket. There is no need to cut away the DATA sockets, as we will be using 0.6" SRAMs for DATA. |
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| Now to prepare the board to accept the machined pin sockets. |
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| Carefully remove the solder from the solder joints. I used a combination of a soldering iron, solder sucker, and a skewer to push out any residual solder. |
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| Once the solder is removed, snap the machined pin sockets into two parts with 14 pins in each. Discard any remainder as they will not be required. |
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| Then solder the new sockets in. |
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| Then simply install your new SRAM chips. The 0.3" 12ns chips are to be used for the TAG memory, and the 0.6" 70ns chips are for the DATA. |
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| Install the 50MHz (or other fast stable crystal). If your board does not have a socketed crystal (most do), you will have to desolder the old crystal and solder a 14 pin IC socket on. This allows for easy testing of new crystals. Also ensure that you set the DIP switch SW1/7 and SW1/8 OFF. This specifies that you have 64K cache. |
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| You will need to remove the old 65816 CPU. The ideal way is to use a PLCC chip puller. However, I managed to remove the CPU quite easily using a small jewellers screwdriver and gently prising the old CPU out via the two larger cut-outs in opposite corners. Then, replace the CPU with the faster one. |
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| Install the ZIP GSX back into your IIgs. You can see from this picture that I have also installed a fan onto the powersupply. I found my accelerated system was overheating after about 40-60 mins of continual use, so I wired up an old CPU fan and attached it to the side of the powersupply. So far it has kept the temperature down adequately. |
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| You should now be good to go. The screenshot here shows that the upgrade was successful. I now have 12.5MHz speed and 64K cache. The IIgs is quite "zippy" at this speed (pardon the pun). |
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