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Virtual Platforms for Memory Controller Design Space Exploration. Matthias Jung , Christian Weis, Norbert Wehn University of Kaiserslautern, Germany. Standard Memory System. Bandwidth Requirements. Memory Wall. CORE. n s. Power hungry I/O transceivers. 16B. m s. m s. L1 private
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Virtual Platforms for Memory Controller Design Space Exploration • Matthias Jung, Christian Weis, Norbert Wehn • University of Kaiserslautern, Germany
Standard Memory System Bandwidth Requirements Memory Wall CORE ns Power hungry I/O transceivers 16B ms ms L1 private cache 64KB L2 private cache 256KB Memory Controller: 3 Channels 512B 64B L3 shared cache 8-12MB . Pin limitation due to package SRAM DRAM HDD/SSD
3D Stacked Wide I/O DRAM • Stacked DRAM dies • TSV connections • Multiple Channels Higher available bandwidth 3D stacked DRAM 1 or 2 Channel DDR3 Memory controller bottleneck MPSoC Increasing bandwidth demand New generation of Memory Controllers is required
Design Space Exploration with Virtual Platforms • Huge design space of 3D-DRAM controller • Flexible and cycle approx. models are needed for fast investigation • RTL simulation is too slow for system level analysis • TLM based virtual platforms with Synopsys Platform Architect Speedup of TLM models up to 377xcompared to CA1 Simulating in seconds instead of hours 1 M. Jung, et al. TLM Modelling of 3D Stacked Wide I/O DRAM Subsystems, in Proc. HiPEAC Conference 2013, Berlin.
Special TLM DRAM Protocol1 • Application specific phases with DECLARE_EXTENDED_PHASE() • Phases derived from DRAM commands (Jedec Wide I/O Standard) • DRAM commands: ACT, PRE, RD, WR, REFA … Example: 1 M. Jung, et al. TLM Modelling of 3D Stacked Wide I/O DRAM Subsystems, HiPEAC, 2013, Berlin.
Experiments and Results • TLM model was compared with cycle accurate SystemC implementation • Tested with Mediabench and CHStone Benchmark traces 42s 1h 41m Speedup up to two magnitudes!
Power Modeling of 3D-DRAM with TLM2.02 Two parts of power consumption: • Background Power • Command Power • DRAM Power states accounted with TLM phases I t ACT WR PRE ACT RD WR PRE 2 M. Jung et al. Power Modelling of 3D-Stacked Memories with TLM2.0, SNUG 2013, Munich
Results (Power Simulation) • TLM model was compared with a cycle accurate SystemC implementation and the standalone power simulator DRAMPower3 • Tested with Mediabench and CHStone Benchmark traces Deviation max 5% to reference models 3www.drampower.info
Current Work: Thermal Simulation • Co-simulation with 3D-ICE Simulator3 • Traces will be generated from GEM54 • Closed Loop Control 3 http://esl.epfl.ch/3d-ice.html 4 http://www.gem5.org/
Conclusion • 3D stacked DRAMs are the future technology • Virtual platform for DSE of new multi-channel Wide I/O DRAM controllers are mandatory • DRAM specific TLM protocol was introduced(can be used for any kind of DRAM) • Precise Power model presented • Early checkpoint for SW implementations • Current and Future Work: Advanced scheduling and arbitration algorithms
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