10NES

The Checking Integrated Circuit, or CIC, is a lockout chip designed for the Nintendo Entertainment System which had three main purposes:

Improved designs of the CIC chip were also used in the later Super Nintendo Entertainment System and Nintendo 64, although running an updated security program which performs additional checks.

The 10NES system is a lock-out system designed for the North American and European versions of the Nintendo Entertainment System (NES) video game console. The chip is a lock which can be opened by a key in the games, designed to restrict the software that could be operated on the system.

Nintendo president Hiroshi Yamauchi said in 1986, "Atari collapsed because they gave too much freedom to third-party developers and the market was swamped with rubbish games." 10NES prevented third-party developers from producing games without Nintendo's approval, and provided the company with licensing fees.

The system consists of two parts, a Sharp Corporation 4-bit microcontroller in the console (the "lock") that checks the inserted cartridge for authentication, and a matching chip in the game cartridge (the "key") that gives the code upon demand. If the cartridge does not provide the authentication, then the CIC resets the CPU during every cycle until a game with the authorization chip is inserted. The constant resetting of the CPU stops the console from booting up.

The program used in the NES CIC is called 10NES and was patented under U.S. Patent 4,799,635. The source code is copyrighted; only Nintendo can produce the authorization chips. The patent covering the 10NES expired on January 24, 2006, although the copyright is still in effect.

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