Pipelined Data Path and Control

PIPELINED DATA PATH AND CONTROL

The Classic Five-Stage Pipeline for a RISC Processor

Each of the clock cycles from the previous section becomes a pipe stage—a cycle in the pipeline.

Each instruction takes 5 clock cycles to complete, during each clock cycle the hardware will initiate a new instruction and will be executing some part of the five different instructions.

3 observations:

1.     Use separate instruction and data memories, which implement with separate instruction and data caches.

2.     The register file is used in the two stages: one for reading in ID and one for writing in WB, need to perform 2 reads and one write every clock cycle.

3.     Does not deal with PC, To start a new instruction every clock, we must increment and store the PC every clock, and this must be done during the IF stage in preparation for the next instruction.

To ensure that instructions in different stages of the pipeline do not interfere with one another. This separation is done by introducing pipeline registers between successive stages of the pipeline, so that at the end of a clock cycle all the results from a given stage are stored into a register that is used as the input to the next stage on the next clock cycle.