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| Blasting the FZ-1 to 4MB |
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| Some of you might have come across an article from Ron Noblett about how to extend the FZ-1 to 4MB using 41256-type DRAMs. I have once extended a Commodore 1764 REU to 2MB this way and I can tell you it's a horrible work. Since you can get 4MB SIMMs from old 386 boards pretty easily it'd be a much better idea to use these instead. | Sad but true... These days one really calls for spam when publishing an email address on a website. But what the heck. |
| Warning (aka "Update 2025") |
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This is a design study. I never built it. Even if you successfully build this hardware, you'd still find yourself restricted to 2MB (1MW) for reasons of OS limitations. I didn't know the latter back then when I designed it some 25 years ago. You'll find some alike designs out there which are seemingly inspired from this very page, but seemingly missed the thing about port wiring, series resistors, or the generally tight timing. No, you cannot just slam an extra ~50ns onto signal generation and hope that this works w/o issues in a ~14MHz timing. Long story short: Take it as some nice idea, some dream, but don't expect it to work the way you hoped it does. |
| Modifying your FZ-1 | ||||||||||||||||||||||||||||||||||||||||
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Casio offers an easy way to extend the FZ-1's memory through the memory expansion slot. However, something seemingly changed between design phase and implementation: Although the FZ-1's sound engine can address up to 4MB (2MW), Casio decided to limit the OS to support only 2MB (1MW), i.e., two disks, and accordingly limit this port to only support an additional 512Mbit*16. To make full use of this slot you need to do some trace cutting and rewiring. And, of course, hack the OS to support 4MB instead of just 2MB. It's also not possible to disable the internal memory from the outside. This would be your second task.
Only RAS2/3 are wired to this port, all others are connected to ground to keep you from messing with the internal memory (RAS0/1) and higher banks (RAS4-7) that are not supported by the OS. Cut the traces going to CASB, RAS0/1 and RAS4-7, they are connected to GND by default. After this step you need to rewire them to the appropriate pins of the GAS chip (uPD65012G074) as shown above. The signals marked with (*) have a 33Ohm resistor connected to GAS. Desolder these for further use. After this step is done build the following circuitry:
 Interfacing 4MB SIMMs to the FZ-1 From the memory expansion connector now wire all address and data lines as well as the write enable signal to the SIMM. Instead of the original RASx and CASB signals use RAS and CAS generated by the above circuitry which also provides additional memory address signals. Now have fun hacking the OS to support the maximum amount of waveform memory accessible by GAA and GAB ... |