The three basic ISA (Instruction Set Architecture) architectures for internal storage in the CPU include cache, RAM, and registers. Cache is a type of high-speed memory that stores frequently used data to speed up the CPU's access. RAM (Random Access Memory) stores data that is currently being processed by the CPU. Registers are small, fast storage locations built into the CPU that hold data used in calculations or data transfers. These three types of internal storage work together to optimize the performance of the CPU, improving its speed and efficiency.