IntermediateTopic 58 of 104Electronics & Embedded
Pipelining
Overlaps instruction stages to increase throughput.
In depth
Pipelining overlaps fetch, decode, execute, memory and write-back stages so throughput approaches one instruction per cycle. Hazards (data, control, structural) cause stalls; solutions are forwarding, branch prediction and stalling. Deeper pipelines raise clock but increase penalty.
Key points
- Speedup ≈ number of stages
- Branch misprediction penalty
- Out-of-order execution
ExampleA 5-stage pipeline completes 1 instruction per cycle after filling.
What is Pipelining?
Overlaps instruction stages to increase throughput.
Why is it important to understand pipelining?
Pipelining improves throughput by overlapping instructions, which is the main reason modern processors run much faster than their clock suggests.
What is a pipeline hazard?
A situation that stops the next instruction from running in its slot, such as a data dependency, a branch or a resource clash.
Why does pipelining not reduce the time for one instruction?
Each instruction still passes through all stages, so its latency stays the same, but more instructions are in flight at once.
How is Pipelining used in practice?
Typical applications include understanding why branches slow down a pipelined processor, speeding up a signal processing loop by keeping the pipeline full and diagnosing a stall caused by a data dependency between instructions.
What should I learn before Pipelining?
Study "Instruction set architectures" first (topic 57 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
What are the key points of Pipelining?
Speedup ≈ number of stages. Branch misprediction penalty. Out-of-order execution.
Can you give an example of Pipelining?
A 5-stage pipeline completes 1 instruction per cycle after filling.
What comes after Pipelining?
The next topic is "Cache memory", which builds directly on this one.
How difficult is Pipelining?
It is classed as Intermediate in Electronics & Embedded (topic 58 of 104). It is an intermediate topic. Work through the beginner topics in Electronics & Embedded first.