Recap: Lecture 7 Lookahead Pipeline Styles

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Recap Lecture 7Lookahead Pipeline Styles

• 2 Strategies
• Early Evaluation
• Early Done

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Lookahead Pipelines Strategy 1

• Use non-neighbor communication
• stage receives information from multiple later
  stages
• allows early evaluation

Benefit stage gets head-start on next cycle
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Lookahead Pipelines Strategy 2

• Use early completion detection
• completion detector moved before stage (not
  after)
• stage indicates early done in parallel with
  computation

early completion detector
Benefit again, stage gets head-start on next
cycle
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Recap Lectures 8Lookahead Pipeline Styles

• Single-Rail Styles

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Lookahead Pipelines Single-Rail

• 5 New Designs
• Dual-Rail Data Signaling
• LP3/1 early evaluation
• LP2/2 early done
• LP2/1 early evaluation early done
• Single-Rail Bundled-Data Signaling
• LPSR2/2 early done
• LPSR2/1 early evaluation early done

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Single-Rail Designs

• Background
• Single-rail uses 1 wire for each data bit

• Simple design (can reuse sync. components)
• Fixed completion time

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Single-Rail Design

• Derivative of PS0, adapted to single-rail
• Bundled-Data matched delays replace completion
  detectors

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Single-Rail Design LPSR2/2

• Derivative of LP2/2, adapted to single-rail

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Single-Rail Design LPSR2/1

• Derivative of LP2/1, adapted to single-rail

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LPSR2/1 Inside a Stage
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LPSR2/1 Protocol
N
N1
N2
N evaluates
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Timing Analysis