However, this time Nintendo went back to multiple chips, with three kinds deployed in NTSC regions (regardless of Japanese or North American releases) and two kinds deployed in PAL regions.

Similar chips were also used in the Super NES, although for the SNES it is likely that all regions use the same chip (the chip only assures that the cartridge was manufactured by Nintendo themselves, and has nothing to do with Region Coding - given that breaking (or filing) off a pair of tabs at the back of a North American SNES' cartridge slot is all it takes to get Japanese games running).

However, the top-loading NES-101 omitted the lockout chips entirely, meaning that theoretically, a game made for the NES-101 may or may not be playable on the original NES-001.

And yes, many Europeans were angry at the fact.

The big kicker is that variants of the 10NES were also used in Europe, and due to the NES' history in Europe there are two different versions of the NES over there, each with its own (incompatible) 10NES chip.

This situation was a factor in Nintendo implementing copy protection into both the American NES and the Famicom Disk System. Similar to what happened to Atari, third party developers flooded the market with low-quality games, and pundits feared a crash of the Japanese video game market similar to the American one. The original Famicom had no lockout chip.

Nintendo promptly sued them in return, winning one of two counts of infringement, but later choosing to settle out of court. Atari/Tengen (ironic, given their earlier role in necessitating such a system to begin with) notably obtained the specs of the chip by (falsely) claiming they needed it for evidence in a legal case of their own, using that information to make a duplicate chip, their 'Rabbit' chip. Regardless, several companies discovered ways to beat the chip, such as piggybacking a chip from a licensed cartridge (Game Genie style) or using a voltage spike to knock out (bypass) the authentication circuit. This was at least in part because of the Atari 2600 and other consoles of the pre-NES era having no lockout controls whatsoever, leading to a market flooded with Shovelware, which was a major factor in The Great Video Game Crash of 1983 Nintendo was obviously keen on avoiding such a situation. Among other things, this allowed Nintendo to keep tight license control (and censorship) over developers attempting to publish games on the console, not just users attempting to make their own copies.

The North American version of the Nintendo Entertainment System used a proprietary (and patented) lockout chip called the 10NES, which reset the CPU if it did not detect a corresponding key chip on the game cartridge.

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