Several factors affect the performance of a CPU. These include clock speed (measured in GHz), which indicates how many cycles per second the CPU can execute; the number of cores, which determines how many tasks the CPU can handle simultaneously; the size of the CPU cache, which affects the speed of data access; and the CPU's architecture and instruction set, which impact how efficiently the CPU can process information. Manufacturers continually evolve CPU designs to enhance performance, power efficiency, and thermal management.