CPS II

Infobox cvg
title= Capcom Play System 2


caption= Super Street Fighter II "B" board
developer= Capcom
publisher= Capcom
released= September 1993
input= 8-way joystick, from 3 to 6 buttons
cabinet= upright
cpu= Motorola 68000 (@ 16 MHz)
sound= Sound CPU: Z80 (@ 8 MHz) Q-Sound (@ 4 MHz)
display= Raster, 384 x 224 pixels (Horizontal), 4096 colors

The nihongo|CPS II|CPシステムII|shīpī shisutemu tsū or Capcom Play System II is an arcade system board that Capcom first used in 1993 for "Super Street Fighter II". It was successor to their previous CPS arcade hardware and was succeeded by the CPS III hardware in vgy|1996.

History

The earlier Capcom system board, CPS-1, while successful, was very vulnerable to bootleggers making unauthorized copies of the games. In order to rectify the situation, Capcom took the CPS-1 hardware (with QSound) with minimal changes and employed encryption on the program ROMs to prevent software piracy.

The CPS-2 consists of 2 separate parts; the "A" board, which connects to the JAMMA harness and contains components common between all CPS-2 games, and the "B" board, which contains the game itself. The relationship between the "A" and "B" board is basically the same as that between a home video game console and cartridge. CPS-2 "A" and "B" boards are color-coded by region, and each board can only be used with its same-colored mate. The exception to this is that the blue and green boards can be used together.

The "B" boards hold battery-backed memory containing decryption keys needed for the games to run. As time passes, these batteries lose their charge and the games stop functioning, because the CPU cannot execute any code without the decryption keys. This is known to hobbyists as the "suicide battery". It is possible to bypass the original battery and swap it out with a new one [ [http://cps2shock.retrogames.com/suicide.html CPS-2 Shock ] ] in-circuit, but this must be done before the original falls below 2V or the keys will be lost.

Due to the heavy encryption, it was believed for a long time that CPS-2 emulation was next to impossible. However, in January 2001, the CPS-2 Shock group [ [http://cps2shock.retrogames.com/wip.html CPS-2 Shock ] ] was able to obtain unencrypted program data by hacking into the hardware, which they distributed as XOR difference tables to produce the unencrypted data from the original ROM images, making emulation possible, as well as restoring cartridges that had been erased because of the suicide system.

In January 2007, the encryption method was fully reverse-engineered by Andreas Naive [ [http://andreasnaive.blogspot.com/ Notas de Andy ] ] and Nicola Salmoria. It has been determined that the encryption employs two four-round Feistel ciphers with a 64-bit key. [ [http://www.mameworld.net/maws/mamesrc/src/mame/machine/cps2crpt.c MAWS - MAME source ] ] [ [http://mamelife.blogspot.com/2007/01/cps2-getting-closer.html Nicola's MAME Ramblings: CPS2 Getting Closer ] ] The algorithm was thereafter implemented in this state for all known CPS-2 games in MAME.

Also thanks to the encryption, the system was never bootlegged until unencrypted program data became available.

Region colors

* Blue: U.S.A., Canada, and Europe
* Green: Japan
* Orange: South America
* Gray: Asia
* Yellow: "Region 0" (available by rental only)
* Black: "Region 0" incorporated "A" and "B" board in the same unit

List of games

ee also

* CPS-1
* CPS-3

References

External links

* [http://www.mameworld.net/maws/mamesrc/src/mame/drivers/cps2.c Technical information in the MAME CPS-2 driver]
* [http://www.jammaboards.com/store/pcb-mods-parts-and-service/cps-2-battery-replacement-kit/prod_65.html CPS-2 Suicide Battery Repair Kit by JAMMABOARDS.COM]
* [http://cps2shock.retrogames.com/techinfo.html CPS-2 Shock - Technical Information]
* [http://www.system16.com/hardware.php?id=795 CPS-2 at System 16 - The Arcade Museum]
* [http://www.jammaparts.com/keystonemod.htm CPS-2 Keystone Suicide Battery Retainer Mod - JAMMAPARTS.COM]