CP System II

• 1. Introduction

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  The CP System II was an arcade board from Capcom, also known as CPS-2 or Capcom Play System 2, and its games could stop working on their own. Nothing had to be broken, and nobody had to tamper with anything. A game that ran perfectly one day could refuse to start on a later day, even for an owner who had done everything by the book.

  Three questions drive this documentary. Why did Capcom want its games to be so hard to copy? How did outsiders finally get inside the board's protection? And what kind of library did the hardware end up carrying during its long working life?

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• 2. Two Boards, One Game

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  A CP System II machine pairs two boards. The A board connects to the JAMMA harness and holds the parts that every CP System II game shares. The B board holds the game itself. Capcom's own arrangement resembles a home console and its cartridge, with the A board in the console's role. The game boards came enclosed in plastic cases.

  Swapping titles never required altering the core hardware, a trait inherited from the original CP System. The earlier hardware had the same flexibility, so an operator could change a cabinet's game without rebuilding it.

  Color told operators where a board belonged. Japan used green plastic with white text on the version screen, while the U.S.A. used blue plastic with red text. Europe and the rest of the world also used blue plastic, but with blue text. Asia received grey plastic with yellow text. The Hispanic market and Brazil both used orange plastic, with green text for one and magenta for the other. Oceania used blue plastic with orange text.

  Each board worked only with a mate of the same color, with one exception. Blue and green boards could be paired. Rental units used yellow plastic, and a black metal all-in-one version also existed.

  Color coding kept legitimate boards in order. A second feature was aimed at keeping outsiders out.

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• 3. The Piracy Problem

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  In 1990, Capcom announced that it was developing the CP System II. The company aimed to finish the hardware in 18 months. It also originally planned for the board to handle 3D graphics.

  Piracy shaped the final design. The original CP System, called CPS-1, had sold well but was very easy prey for bootleggers who made unauthorized copies of games. Capcom took that earlier hardware, including its QSound audio, and changed very little. The big addition was encryption on the program ROMs, so that a copied game would not run.

  The strategy worked. While the encryption held, the system stayed free of bootleg copies. The new board also sat at the end of a family line, succeeding the CP System, the CP System Dash and the Capcom Power System Changer hardware.

  Where Capcom chose to keep the decryption keys turned out to matter just as much as the encryption itself.

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• 4. The Suicide Battery

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  Below 2 volts, a CP System II game could lose its keys for good. Those keys live in battery-backed memory on the B board. As the battery slowly loses its charge, the games stop functioning, because the processor cannot run any code without the keys. Enthusiasts call this arrangement a suicide battery.

  A remedy exists, but it has a deadline. The original battery can be bypassed and a fresh one swapped in while still connected to the board. That must happen before the old battery drops under 2V, or the keys vanish.

  The design had a stark consequence. A board used entirely legally would still stop playing after a finite time, unless a fee was paid to Capcom to replace the battery.

  That limited lifespan is the problem the engineers in the next chapter would eventually solve for good.

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• 5. Cracking the Code

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  For a long time, the heavy encryption made people believe that emulating the CP System II was next to impossible. In January 2001, a group called CPS-2 Shock proved otherwise. They hacked into the hardware and obtained unencrypted program data. They shared it as XOR difference tables, which rebuild the unencrypted data from the original ROM images. The tables made emulation possible. They also restored cartridges that the suicide system had erased.

  January 2007 brought a complete answer. Andreas Naive and Nicola Salmoria fully reverse-engineered the encryption method. They found two four-round Feistel ciphers using a 64-bit key. The algorithm was then built into MAME for all known CPS-2 games.

  In April 2016, Eduardo Cruz, Artemio Urbina and Ian Court announced that they had reverse engineered Capcom's security programming for the board. Their work allowed any dead game to be restored cleanly, a process called de-suicide, with no hardware modifications.

  The chip at the center of the whole lock was the DL-1525, a Capcom-made version of the 68000 processor.

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• 6. Chips and Pixels

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  On screen, the board drew an active picture of 384 by 224 pixels, inside an overscan area of 512 by 262 with 262 scanlines. Up to 900 sprites could appear at once. The palette held 16,777,216 colors, with 256 levels of alpha transparency. Only 4096 colors could show on screen together, and each tile was limited to 16.

  The main processor ran at 16 MHz. Beside it sat a sound processor at 8 MHz, either a Kabuki DL-030P or a standard Z80. The Kabuki chip was an encrypted Z80, though its encryption went unused.

  Graphics came from the CPS-A and CPS-B processors, running at 16 MHz and identical to those in the CPS-1. Sound came from a Lucent DL-1425 Q1 QSound DSP16A at 4 MHz. Two more Capcom parts handled the rest. The DL-2227 refreshed the memory, and the DL-1123 managed input and output.

  Total memory came to 1328 KB, made of 1 MB of FPM DRAM and 304 KB of SRAM. The A board carried 1 MB of DRAM and 280 KB of SRAM, split into 256 KB for video, 16 KB for input and output, and 8 KB for sound. The B board added 16 KB of SRAM, in two 8 KB chips. A communication board held another 8 KB. Paired together, the A and B boards measured 40 by 27 by 8 centimeters.

  That 322 Mbit ceiling, equal to 40.25 MB, was the space every game on the board had to fit inside.

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• 7. A Varied Library

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  Forty-one games appear on the CP System II list, and the first, Super Street Fighter II: The New Challengers, arrived on the 9th of September 1993. It also gave the board its debut. Head-to-head fighting games fill much of the list from there. Darkstalkers: The Night Warriors followed on the 5th of July 1994, and X-Men: Children of the Atom on the 8th of December 1994. Street Fighter Alpha arrived on the 5th of June 1995.

  Capcom's crossover titles gave the fighters famous opponents. Marvel Super Heroes came on the 24th of October 1995, and X-Men vs. Street Fighter on the 9th of September 1996. Marvel vs. Capcom: Clash of Super Heroes reached the board on the 12th of January 1998, and Street Fighter Alpha 3 that June.

  Beat 'em ups gave the board a different pace. Dungeons & Dragons: Tower of Doom appeared on the 13th of January 1994, and Alien vs. Predator on the 20th of May 1994. Dungeons & Dragons: Shadow over Mystara followed on the 6th of February 1996.

  The range went well beyond brawlers. Eco Fighters, a shoot 'em up, came out on the 12th of December 1993. Mega Man: The Power Battle arrived on the 22nd of September 1995, and Super Puzzle Fighter II Turbo on the 29th of May 1996. Capcom Sports Club brought a sports game on the 22nd of July 1997. Quiz Nanairo Dreams offered a quiz game.

  Outside studios also published games for the hardware. Takumi made Giga Wing and Mars Matrix, and Eighting/Raizing made Dimahoo and 1944: The Loop Master. Mitchell contributed Mighty! Pang, Puzz Loop 2 and Janpai Puzzle Chōkō, while Cave made Progear.

  The last third-party game, Janpai Puzzle Chōkō from Mitchell, reached the board on the 20th of August 2001.

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• 8. A Long Goodbye

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  More than two years after that last outside release, Capcom closed the book on new hardware. On the 22nd of December 2003, it ceased manufacturing the CP System II. Hyper Street Fighter II: The Anniversary Edition, the final game released for the board, shared that date.

  The board's successor, the CP System III, had arrived in 1996. The CP System II outlasted that successor by over four years.

  On the 31st of March 2015, Capcom ended most technical support for the hardware and its games. Battery replacements, the one service the board's design made essential, carried on past that. They ended on the 28th of February 2019, closing all official support.

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