PipelineDesign

Pipelined design is a technique for organizing a process into a chain of sequential stages, with registers between stages to hold intermediate results. Each stage performs part of the overall task, allowing different items to move through the pipeline at overlapping times. Pipelining is widely used in hardware design, such as CPUs and digital signal processing, as well as in software and data processing pipelines.

In hardware pipelines, the clocked stages communicate via registers. After the pipeline is filled, a new item completes per clock cycle in an ideal case, increasing throughput, though overall latency for a single item grows with the number of stages. The depth of the pipeline and the balance of workload across stages determine performance and power consumption. Proper timing and synchronization are essential to ensure correct operation across all stages.

Common examples include CPU instruction pipelines (fetch, decode, execute, memory access, write-back), graphics pipelines, and streaming data paths in DSPs and network devices. Software pipelines appear in streaming frameworks and data processing workflows where producers, transformers, and consumers operate in stages.

Key challenges include hazards: data hazards when a stage depends on results from a previous stage, control hazards from branches, and resource conflicts (structural hazards). Techniques to mitigate hazards include forwarding (data transfer between stages), hazard detection units, branch prediction, and pipeline stalls or bubbles. Design decisions also involve balancing stage times to minimize idle cycles and managing latency introduced by multiple stages.

Overall, pipelined design improves throughput and resource utilization but increases design complexity, area, and power, with diminishing returns as depth grows.