TLDR: The CPU pipeline structure is a design technique in processor architecture that allows multiple instructions to be executed simultaneously by dividing the processing cycle into discrete stages. Each stage performs a specific part of the instruction execution process, such as fetching, decoding, executing, and writing back results. This approach, introduced in early processors like the Intel 8086 in 1978, improves overall performance by maximizing resource utilization and instruction throughput.
https://en.wikipedia.org/wiki/Instruction_pipelining
A typical CPU pipeline structure consists of stages such as instruction fetch, instruction decode, operand fetch, CPU execute, and write-back. By processing multiple instructions concurrently, pipelines enable a form of parallelism within a single core. For example, while one instruction is being executed, the next can be decoded, and another can be fetched. Modern CPUs employ deep pipelines with more stages to handle complex instructions and optimize performance, though this can introduce challenges like pipeline stalls due to dependencies or branch mispredictions.
https://www.intel.com/content/www/us/en/architecture-and-technology/branch-prediction.html
Advanced techniques like superscalar execution and out-of-order execution enhance the efficiency of CPU pipeline structures by allowing multiple instructions to progress through the pipeline simultaneously and in a non-sequential order. These features, combined with mechanisms like branch prediction and speculative execution, minimize idle time and maximize throughput. The evolution of pipeline structures continues to shape CPU design, enabling processors to meet the growing demands of modern software workloads.