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In a standard five-stage pipeline, during the decoding stage, the control unit will determine whether the decoded instruction reads from a register to which the currently executed instruction writes. If this condition holds, the control unit will stall the instruction by one clock cycle.
Avoid illegal or semantically ambiguous operations (typically involving subtle instruction pipeline timing issues or non-interlocked resources). The pipeline stalls can be caused by structural hazards (processor resource limit), data hazards (output of one instruction needed by another instruction) and control hazards (branching).
Bubbling the pipeline, also termed a pipeline break or pipeline stall, is a method to preclude data, structural, and branch hazards. As instructions are fetched, control logic determines whether a hazard could/will occur. If this is true, then the control logic inserts no operation s (NOP s) into the pipeline. Thus, before the next instruction ...
In computer engineering, instruction pipelining is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing incoming instructions into a series of sequential steps (the eponymous "pipeline") performed by different processor units with different parts of instructions ...
When a next-line predictor points to aligned groups of 2, 4, or 8 instructions, the branch target will usually not be the first instruction fetched, and so the initial instructions fetched are wasted. Assuming for simplicity, a uniform distribution of branch targets, 0.5, 1.5, and 3.5 instructions fetched are discarded, respectively.
The main common concept of each design is a five-stage execution instruction pipeline. During operation, each pipeline stage works on one instruction at a time. Each of these stages consists of a set of flip-flops to hold state, and combinational logic that operates on the outputs of those flip-flops.
Operand forwarding (or data forwarding) is an optimization in pipelined CPUs to limit performance deficits which occur due to pipeline stalls. [1] [2] A data hazard can lead to a pipeline stall when the current operation has to wait for the results of an earlier operation which has not yet finished.
In computing, a pipeline or data pipeline [1] is a set of data processing elements connected in series, where the output of one element is the input of the next one. The elements of a pipeline are often executed in parallel or in time-sliced fashion. Some amount of buffer storage is often inserted between elements. Computer-related pipelines ...