The Famicom contained no lockout hardware and, as a result, unlicensed cartridges (both legitimate and bootleg) were extremely common throughout Japan and the Far East. The original NES (but not the top-loading NES-101) contained the 10NES lockout chip, which significantly increased the challenges faced by unlicensed developers. Tinkerers at home in later years discovered that disassembling the NES and cutting the fourth pin of the lockout chip would change the chip’s mode of operation from "lock" to "key", removing all effects and greatly improving the console’s ability to play legal games, as well as bootlegs and converted imports. NES consoles sold in different regions had different lockout chips, so games marketed in one region would not work on consoles from another region. Known regions are: USA/Canada (3193 lockout chip), most of Europe (3195), Asia (3196) and UK, Italy and Australia (3197). Since two types of lockout chip were used in Europe, European NES game boxes often had an "A" or "B" letter on the front, indicating whether the game is compatible with UK/Italian/Australian consoles (A), or the rest of Europe (B). Rest-of-Europe games typically had text on the box stating "This game is not compatible with the Mattel or NES versions of the Nintendo Entertainment System". Similarly, UK/Italy/Australia games stated "This game is only compatible with the Mattel or NES versions of the Nintendo Entertainment System".

What did the Famicom sorely lack?