CP System II

Lore & Background

Capcom announced the development of the CP System II in 1990, planning to complete it in 18 months with original plans for 3D graphics capability. The earlier CP System (CPS-1) was vulnerable to bootleggers making unauthorized copies, so Capcom took the CP System hardware with QSound, made minimal changes, and employed encryption on the program ROMs to prevent software piracy. Due to the encryption, the system was never bootlegged until unencrypted program data became available.

The CP System II consists of two separate parts: the A board, which connects to the JAMMA harness and contains common components, and the B board, which contains the game itself. The relationship is similar to that between a home console and cartridge. A and B boards are color-coded by region, and each board can only be used with its same-colored mate, except that blue and green boards can be used together. The B boards hold battery-backed memory containing decryption keys; as batteries lose charge, the games stop functioning, a phenomenon called a 'suicide battery'. It is possible to bypass the original battery and swap it out in-circuit before it falls below 2V, or the keys are lost.

Due to heavy encryption, CPS-2 emulation was long believed impossible. In January 2001, the CPS-2 Shock group obtained unencrypted program data by hacking into the hardware, distributing XOR difference tables to produce unencrypted data from original ROM images, enabling emulation and restoration of erased cartridges. In January 2007, the encryption method was fully reverse-engineered by Andreas Naive and Nicola Salmoria, revealing two four-round Feistel ciphers with a 64-bit key. In April 2016, Eduardo Cruz, Artemio Urbina and Ian Court announced successful reverse engineering of the security programming, enabling clean 'de-suicide' restoration of dead games without hardware modifications.

Reader's Guide

The CP System II's significance lies in its response to rampant bootlegging of the earlier CPS-1 hardware. By encrypting program ROMs and storing decryption keys in battery-backed memory, Capcom created a system that was effectively immune to unauthorized copying until unencrypted data was obtained years later. This encryption, however, introduced a built-in obsolescence: the 'suicide battery' meant that every legitimate board would eventually stop functioning unless the battery was replaced before it dropped below 2V, and Capcom charged a fee for official replacements. The system's longevity is notable—new games were released until 2003, and official support continued until 2019, long after its successor CPS-3 had been introduced. The eventual reverse engineering of the encryption by hobbyists and the CPS-2 Shock group allowed emulation and restoration of dead boards, preserving a library of 41 games that includes iconic titles like Super Street Fighter II and Hyper Street Fighter II. The system's architecture, with separate A and B boards color-coded by region, and its use of QSound audio, made it a distinctive and influential platform in arcade history.

Did You Know?

• The CP System II was announced in 1990 with original plans for 3D graphics capability.
• Games are encrypted and require a decryption key stored in battery-backed memory on the main board to run.
• Capcom ended battery replacements for the hardware on February 28, 2019, ending all official support.