Capcom’s CPS2 – or CP System II – was the early to mid-90s arcade hardware famous for Super Street Fighter II, Alien vs. Predator, and a few of the Marvel and Capcom crossover arcade games. As you would expect, these boards have become collectors items. Unfortunately for future generations, Capcom took some short-sighted security measures to prevent copying the games, and the boards have been failing over the last two decades.

After months of work, [ArcadeHacker] and several other arcade enthusiasts have reverse engineered the security protocol and devised a method of de-suiciding these arcade boards, allowing for the preservation of this hardware and these games. The code that does the trick is up on GitHub.

Last year, [ArcadeHacker] reverse engineered the on-chip security for Capcom’s Kabuki processor, the CPU used in some of Capcom’s earlier arcade boards. It used a similar protection scheme. In the Kabuki hardware, the on-chip ROM was interspersed with a few XOR gates on the processor’s bus. With a security key kept in battery-backed memory, this was enough to keep the code for the game secret, albeit at the cost of preventing historical preservation.

Over the next few weeks, [ArcadeHacker] will post more detailed information about the copy protection scheme of the CPS2 board, but the proof-of-concept works right now. It’s now possible to revive a CPS2 board that has killed itself due to a dead battery, and the hardware is as simple as an Arduino and a few test clips. You can check out a video of the exploit in action below.

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