Nintendo Entertainment System Sat May 04 2002 at 17:19:35 With this discussion of the NES technical specs, everyone has forgotten possibly the most important chip in the box, the “lockout” chip. The lockout chip was Nintendo's method of controlling what NES-compatible games were manufactured. A microchip inside the NES ran a program called “10NES” that prevented all cartridges from functioning unless they contained a similar chip. Since this "authenticating processor" was a Nintendo patent, only Nintendo could legally provide the component to companies who wished to produce NES-compatible cartridges. Nintendo would grant licenses to software developers and then manufacture the actual cartridges themselves, ensuring that the specs for the chip remained a secret.