CPE 431531 Chapter 6 Enhancing Performance with Pipelining

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CPE 431/531Chapter 6 - Enhancing Performance
with Pipelining

• Swathi T. Gurumani
• Modified From Slides of
• Dr. Rhonda Kay Gaede
• UAH

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6.1 An Overview of Pipelining -Control Hazards
Stalling
Performance of Stall on Branch Example on Pg.
380 Branch prediction Method of resolving a
branch hazard that assumes a given outcome for
the branch and proceeds from that assumption
rather than waiting to ascertain the actual
outcome Prediction to handle branches untaken,
taken
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6.1 An Overview of Pipelining -Control Hazards
Prediction
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6.2 A Pipelined Datapath Identifying the Stages
Control hazard
Data hazard
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6.2 A Pipelined Datapath Representing Multiple
Instruction Execution
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6.2 A Pipelined Datapath - Adding Pipeline
Registers
128
64
97
64
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6.2 A Pipelined Datapath lw Instruction
Execution IF Stage
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6.2 A Pipelined Datapath lw Instruction
Execution ID Stage
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6.2 A Pipelined Datapath- lw Instruction
Execution EX Stage
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6.2 A Pipelined Datapath - lw Instruction
Execution MEM Stage

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6.2 A Pipelined Datapath - lw Instruction
Execution WB Stage

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6.2 A Pipelined Datapath - sw Instruction
Exection EX stage
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6.2 A Pipelined Datapath sw Instruction
Exection MEM stage
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6.2 A Pipelined Datapath - sw Instruction
Exection WB stage
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6.2 A Pipelined Datapath - Additions for lw and
R-type
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6.2 A Pipelined Datapath - Datapath used by lw
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6.2 A Pipelined Datapath - Stylized Multiple
Clock Cycle Diagrams
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6.2 A Pipelined Datapath - Traditional Multiple
Clock Cycle Diagrams
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6.2 A Pipelined Datapath - Single Cycle Diagram
Cycle 5 Slice
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6.3 Pipelined Control - Identifying Control
Lines Needed
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6.3 Pipelined Control Generating and Saving
Control Lines

• EX - 4
• MEM - 3
• WB - 2

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6.3 Pipelined Control - Putting it all Together
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6.4 Data Hazards and Forwarding - Data
Dependencies

• In the previous example, there were no data
  dependencies. Now, the rest of the story.
• sub 2, 1, 3
• and 12, 2, 5
• or 13, 6, 2,
• add 14, 2, 2
• sw 15, 100(2)

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6.4 Data Hazards and Forwarding - Which Data
Dependencies are Hazards?

• A multiple-clock-cycle diagram is useful for
  looking at the effects of data dependencies.

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6.4 Data Hazards and Forwarding - Classifying
Hazards

• Type 1 The information needed in the EX stage
  by an instruction is the result of the
  instruction one stage ahead (found in the EX/MEM
  pipeline register)
• A. The information is needed in Rrs
• B. The information is needed as Rrt
• Type 2 The information needed in the EX stage
  by an instruction is the result of the
  instruction two stages ahead (found in the MEM/WB
  pipeline register)
• A. The information is needed in Rrs
• B. The information is needed as Rrt