Tuesday, 16 June 2015

Capcom CPS1 - Part 3

Welcome to the third and last post in the Capcom CPS-1 reverse engineering series, if you missed any of the previous readings you can find them here:

Security inside

As explored during the previous two articles, with the introduction of CPS-1 Capcom developed a couple of graphic custom chips known as CPS-A and CPS-B. These chips unified many graphic functions and allowed Capcom to push its game capabilities further while reducing system design complexity.

One specific mission of custom CPS-B was security, a characteristic that prevented operators from reusing CPS-1 hardware by simply burning new roms, this was accomplished by featuring a unique internal chip configuration in almost every new game title.

While early CPS-B chips are truly unique items, with their internal configuration set at the silicon level, the final CPS-B revision known as B-21 was capable of holding any factory configuration by using internal memory backed by an external battery. This helped Capcom simplify its operation by not having to manufacture new CPS-B chips with every new release.

At production one specific configuration was defined by Capcom for the accompanying game title, and losing power supplied by the external battery means you lose your game, a typical problem faced by today's game collector in preserving working original games.