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caius

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The 'GXC-0x' (where 'x' suffix can be 1, 2 ,3, or 4) is a custom IC in DIP40 package found on some Taito/Toaplan arcade PCBs and used as protection :

GXC-02_Wardner.jpg

GXC-04_Demon%2527s%2BWorld.jpg

GXC-04_Twin%2BCobra.jpg

As you can see from above pictures the chip has three rows of markings but only the first two matters so the ICs with same first two rows but different third one are actually interchangeable.Here's the board list and labelling of each revision of the chip (info taken from MAME source)


MAME_info.jpg


Electronically speaking it's a TMS320C010 DSP co-processor in disguise with internal MASK ROM.Recently the internal code has been dumped from all revisions and added to MAME, you can read more about here :

Extracting the elusive TMS32010 mask ROM

This achievement opened the way for possible replacements of this custom IC simply using a not windowed/not erasable version of TMS320C10 and having it execute the code from an external memory.Here, for example, one made recently :

Toaplan/Taito GXC-0x MCU replacement

For my reproduction I decided to adopt a different design using a single ROM to store the external code of the MCU (instead of having two ROMs with deinterleaved lower and upper bytes), this allowed me to obtain a smaller and compact board :

GC-0x_reproduction.jpg

Like other replacements you can set via dispwitches the desidered MCU accordingly to the one used by the PCB. Here's testing of the reproduction on different boards.

Set as 'GXC-02' on Wardner/Pyros PCB :

View: https://youtu.be/JHLTLfwuhm4


Set as 'GXC-03' on Kyuukyoku Tiger PCB :

View: https://youtu.be/J9IknnY-d0A


Set as 'GXC-04' on Twin Cobra PCB:

View: https://youtu.be/cy6PV4tqVZk


Set as 'GXC-04' on Demon's World/Horror Story PCB:

View: https://youtu.be/kCwrWkG-BqQ
 
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