Non Redundant Data Cache

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Non Redundant Data Cache
ISLPED03, Seoul (Korea) - August 25-27, 2003

• Carlos Molina, Carles Aliagas and Montse García
• Universitat Rovira i Virgili Tarragona,
  Spaincmolina,caliagas,mgarciaf_at_etse.urv.es
• Antonio González and Jordi Tubella
• Universitat Politècnica de Catalunya Barcelona,
  Spain antonio,jordit_at_ac.upc.es

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Motivation

• Caches spend close to 50 of total die area

• Caches may be responsible for 10 to 20 of total
  power dissipated by a processor

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Data Value Replication
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Data Value Replication
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Objective

• To reduce die area
• But mantaining miss ratio
• Latency
• Energy consumption

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Conventional Cache

• If (Value AValue B) then Value Redundancy

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Non Redundant Data Cache (1)
Pointer Table
Value Table
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Data Value Inlining

• Some values can be represented with a small
  number of bits (Narrow Values)
• Narrow values can be inlined into pointer area
• Simple sign extension is applied
• Benefits
• enlarges logical capacity of VT
• reduces latency
• reduces power dissipation

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Non Redundant Data Cache (2)
Pointer Table
Value Table
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Simulation Enviroment

• Simulators
• Cacti tool version 3.0 (Static Analysis)
• Alpha version of SimpleScalar 3.0 (Dynamic
  Analysis)
• Benchmarks
• Spec2000
• Maximum Optimization Level
• DEC C F77 compilers with -non_shared -O5
• Statistics Collected for 1 billion instructions
• Skipping initializations

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Inlining Performance
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Die Area
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Latency
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Energy Consumption
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Miss Rate vs Die Area




Miss Ratio




0,1
0,5 1,0 cm2
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Results

• Caches ranging from 256 KB to 4 MB

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Conclusions

• High degree of value replication is present in
  conventional caches
• Non redundant data cache
• Data value inlining
• Die area reduction
• Energy consumption reduction
• Access time reduction
• Minor miss ratio increasing

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Non Redundant Data Cache
ISLPED03, Seoul (Korea) - August 25-27, 2003

• Carlos Molina, Carles Aliagas and Montse García
• Universitat Rovira i Virgili Tarragona,
  Spaincmolina,caliagas,mgarciaf_at_etse.urv.es
• Antonio González and Jordi Tubella
• Universitat Politècnica de Catalunya Barcelona,
  Spain antonio,jordit_at_ac.upc.es