Resurrecting Capcom’s Kabuki

About a dozen old Capcom arcade titles were designed to run on a custom CPU. It was called the Kabuki, and although most of the core was a standard Z80, a significant portion of the die was dedicated to security. The problem back then was arcade board clones, and when the power was removed from a Kabuki CPU, the memory contents of this security setup were lost, the game wouldn’t play, and 20 years later, people writing emulators were tearing their hair out.

Now that these games are decades old, the on-chip security for the Kabuki CPU is a problem for those who have taken up the task of preserving these old games. However, now these CPUs can be decuicided, programming the chip and placing them in an arcade board without losing their memory contents.

Earlier we saw [ArcadeHacker] a.k.a. [Eduardo]’s efforts to resurrect these old CPUs. He was able to run new code on the Kabuki, but to run the original, unmodified ROMs that came in these arcade games required hardware. Now [ArcadeHacker] has it.

The setup consists of a chip clip that clamps over the Kabuki CPU. With a little bit of Arduino code, the security keys for original, unmodified ROMs can be flashed, put into the arcade board (where the contents of the memory are backed up by a battery), and the clip released. [ArcadeHacker] figures this is how each arcade board was programmed in the factory.

If you’re looking for an in-depth technical description of how to program a Kabuki, [ArcadeHacker] has an incredibly detailed PDF right here.

31 thoughts on “Resurrecting Capcom’s Kabuki

  1. I love how language adapts in those kind of niche subjects. Of course, “suicide” is a noun. “This CPU is now suicide” makes it an adjective. “The CPU suicides” and it becomes a verb. And “desuicide” is a entirely new word sparkling with meaning. Lovely.

        1. [ArcadeHacker] didn’t, the entire arcade machine enthusiast community did. There are quite a lot of arcade games other than the ones that use the Kabuki CPU that rely on secret keys preserved by a battery.

  2. He needs to take more care handling those vintage boards and chips like that. Without wearing an ESD strap at all times, there will inevitably be mysterious failures somewhere down the line, and that foam is a big no-no.

  3. Does anyone else think it is incredible that he discovered the security key by examining the logic gates in the actual chip? It makes sense, but man, thats some tenacity! Great PDF by the way.

  4. This device in the article is totally not needed. The kabuki is a custom Z80 cpu. It can be replaced with a standard Z80 and decrypted roms. You will also need to remove resistor 33 and the battery as well and remove pin 30 on h14 and jumper it to pin 27. Then jumper a few more places that I can’t remember off the top of my head. This will work for all kabuki boards. Here is a video of a kabuki I brought back from the dead

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