UPC Non Redundant Data Cache Carlos Molina, Carles Aliagas and Montse García Universitat Rovira i Virgili – Tarragona, Spain Antonio González and Jordi Tubella Universitat Politècnica de Catalunya – Barcelona, Spain ISLPED´03, Seoul (Korea) - August 25-27, 2003
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
Data Value Replication
Objective To reduce die area But mantaining miss ratio Latency Energy consumption
Conventional Cache If (Value A==Value B) then Value Redundancy Value A Value B Tag X Tag Y
Non Redundant Data Cache (1) Pointer Table Value Table Tag X Tag Y Die Area Reduction Tag X Tag Y Additional Hardware: Pointers Additional Hardware: Counters 12345count
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
Tag X Tag Y 10count Non Redundant Data Cache (2) Pointer Table Value Table count Tag X Tag Y 10
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
Inlining Performance
Die Area
Latency
Energy Consumption
Miss Rate vs Die Area | | | 0,1 0,5 1,0 cm 2 Miss Ratio % % % % % % % %
Results Caches ranging from 256 KB to 4 MB
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
UPC Non Redundant Data Cache Carlos Molina, Carles Aliagas and Montse García Universitat Rovira i Virgili – Tarragona, Spain Antonio González and Jordi Tubella Universitat Politècnica de Catalunya – Barcelona, Spain ISLPED´03, Seoul (Korea) - August 25-27, 2003