This document discusses different types of special tuned registers used in CPUs, including control registers, status registers, floating-point registers, and SIMD registers. It explains that special tuned registers are used to hold operands, results, and temporary data and to track the currently executing instruction. Special tuned registers are designated for special purposes like the stack pointer and program counter, whereas general purpose registers hold temporary data during operations. The document also covers advantages like faster access and optimized memory utilization and disadvantages like limited capacity and increased CPU cost.