GameBooster 64 (USA) (v1.1) (Unl), known in Japan as GameBooster 64: Kaizō Version (ジェイムブースター64 改造バージョン), is a popular game enhancement tool for the Nintendo 64 (N64) console. Developed by the Japanese company Agetec, this tool allows users to make modifications to the N64 game cartridges, such as adding extra features, unlocking hidden levels, and increasing the speed of the game. It also allows users to back up their original game cartridges, as well as create their own custom game cartridges. GameBooster 64 is easy to use, and it comes with a comprehensive manual that explains all of the features and how to use them. With GameBooster 64, users can create their own unique gaming experience, and make the most out of their N64 game cartridges.