pipelining

1 definition found

pipelining - Free On-line Dictionary of Computing (26 May 2007) :

  pipeline
  pipelined
  pipelining
  
     <architecture> A sequence of functional units ("stages")
     which performs a task in several steps, like an assembly line
     in a factory.  Each functional unit takes inputs and produces
     outputs which are stored in its output buffer.  One stage's
     output buffer is the next stage's input buffer.  This
     arrangement allows all the stages to work in parallel thus
     giving greater throughput than if each input had to pass
     through the whole pipeline before the next input could enter.
  
     The costs are greater latency and complexity due to the need
     to synchronise the stages in some way so that different inputs
     do not interfere.  The pipeline will only work at full
     efficiency if it can be filled and emptied at the same rate
     that it can process.
  
     Pipelines may be synchronous or asynchronous.  A synchronous
     pipeline has a master clock and each stage must complete its
     work within one cycle.  The minimum clock period is thus
     determined by the slowest stage.  An asynchronous pipeline
     requires handshaking between stages so that a new output is
     not written to the interstage buffer before the previous one
     has been used.
  
     Many CPUs are arranged as one or more pipelines, with
     different stages performing tasks such as fetch instruction,
     decode instruction, fetch arguments, arithmetic operations,
     store results.  For maximum performance, these rely on a
     continuous stream of instructions fetched from sequential
     locations in memory.  Pipelining is often combined with
     instruction prefetch in an attempt to keep the pipeline
     busy.
  
     When a branch is taken, the contents of early stages will
     contain instructions from locations after the branch which
     should not be executed.  The pipeline then has to be flushed
     and reloaded.  This is known as a pipeline break.
  
     (1996-10-13)