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The CPS-2 arcade board contains a suicide battery that will force the board to kill itself when it runs below a certain power threshold.

enter image description here

Supposedly this was created to mitigate piracy of the games, as well as bootleg boards, but wouldn't bootleggers just make their boards without the suicide system?

In addition, once the battery runs out on an official board it no longer works, which makes its inclusion even more puzzling. What was the point of this?

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    Have you searched on the web about it? Even Wikipedia has a decent explanation what it is about.
    – UncleBod
    Oct 26, 2021 at 10:36
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    Maybe the OP is misled by the overly-dramatic term 'suicide battery', as if its purpose is to kill the board, rather than (as is apparent from the Wikipedia article) keeping the board alive.
    – another-dave
    Oct 26, 2021 at 11:58
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    Re: "once the battery runs out..." I once worked for a company that had a manufacturing test fixture built upon an ancient predecessor of this micro. Out of curiosity one day, I asked to see the source code. Nobody knew if we still had it. Who built the fixture? Oh, he left the company years ago. Upon investigating, I was horrified to discover that the only thing keeping the program alive was the SRAM backup battery, which was, by then, almost a decade old.
    – Solomon Slow
    Oct 26, 2021 at 14:04
  • I assume it's an early form of planned obscelescence, which basically means making it so that a product stops working after a certain amount of time.
    – user26627
    Jan 31 at 0:45

1 Answer 1

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This was an anti-piracy measure. If a "bootlegger" wanted to duplicate the board, they would only have access to encrypted ROMs, thus making it impossible to reproduce the arcade board with the software comprising the actual game.

CPS-2 piracy protection used a security key stored in on-chip volatile memory. This is what the battery was keeping powered. When the battery eventually falls below ~2V, the security key is permanently lost.

But there's more. A special-version CPU includes the necessary hardware decryption to use the key and decrypt the game ROM at runtime. So, the system is actually CPU/hardware+encrypted game ROM+security key. A "bootlegger" having no ability to access the key would be blocked from pirating the game, even if they could get a CAPCOM CPU and encrypted copy of the game ROM.

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    The key would be stored in SRAM, rather than EEPROM, and the SRAM in question would generally be on the same chip as the CPU. While many systems use security keys stored in EEPROM, such systems are vulnerable to motivated attacker who remove the top of the package and place extremely fine probes to sense voltages on the chip. Even if the EEPROM itself is protected under layers of metal, the circuitry that accesses it would often not be. Using SRAM would make it very hard for someone to remove the top of the chip without disturbing the memory contents.
    – supercat
    Oct 26, 2021 at 16:42
  • @supercat Thx. I corrected my answer.
    – Brian H
    Oct 26, 2021 at 17:50

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