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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.

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Modifying your FZ-1

Casio offers an easy way to extend the FZ-1's memory through the memory expansion slot. However, although the FZ-1 can address up to 4MB Casio in their eternal wisdom decided to cripple this port to only 512kBx16 allowing 1MBx16 in total. To make full use of this slot you need to do some trace cutting and rewiring.

Pin #Signal
36-21 D0-D15
1,5/6,8,4,2,7,3,9 MA1-MA9
14-16,13,18/17,20/19 RAS0-RAS7
12 WE
37 Vdd
39 digital GND
40 chassis GND
Memory Expansion Port Pinout
SignalPin #
CASB (*)30
RAS0 (*)40
RAS1 (*)39
GAS Pinout

Only RAS2/3 are wired to this port, all others are connected to ground making an easy expansion impossible. Thank you for that, Casio!

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:

SIMM Interface
Interfacing 4MB SIMMs to the FZ-1

From the memory expansion connector now wire all address and data lines aswell as the write enable signal to the SIMM. Instead of the original RASx and CASB signals use RAS and CAS generated from the above circuitry which also provides additional memory address signals.