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Power Visualization, Analysis, and Optimization Tools for FPGAs. Matthew French, Li Wang and Michael Wirthlin USC, Information Sciences Institute, BYU. Outline . Introduction Background JDHL Tool Suite Power Visualization Power Analysis Tools Power Modeling Power Optimization Conclusion.

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power visualization analysis and optimization tools for fpgas

Power Visualization, Analysis, and Optimization Tools for FPGAs

Matthew French, Li Wang and Michael Wirthlin

USC, Information Sciences Institute, BYU

outline
Outline
  • Introduction
  • Background
  • JDHL Tool Suite
  • Power Visualization
  • Power Analysis Tools
  • Power Modeling
  • Power Optimization
  • Conclusion
introduction
Introduction
  • Many devices demand low power in order to increase functional lifetime
    • CLBs max operating frequency rapidly (exponentially) increasing
    • Operating voltages decreasing much slower
  • Result: Exponentially increasing maximum power consumption per device
low power intelligent tool environment
Low-Power Intelligent Tool Environment
  • Object oriented tool set for Power Visualization via JHDL
  • Uses:
    • Circuit logic
    • FPGA architecture
    • Power information
slide5
LITE
  • Take models and power analysis tools and create a power optimization algorithm
    • Algorithm development is supported through the user of tools to query and sort circuit characteristics and drop in COTS CAD tool compliant constraints.
background
Background
  • Low Power FPGA Designs
    • Address VLSI designs of FPGAs
  • Synthesis-Level power optimizations
    • Mapping to LUT-based FPGA techniques
    • Reduce glitching power through pipelining
  • CAD algorithms for PAR
background1
Background
  • Offer “point” solutions
    • Little user control / feedback
  • Synthesis - PAR optimized for Speed / Area
  • Current tools limited
    • Readability
    • Entry point in FPGA design flow
  • Current estimates:
    • Manually estimating
fpga s in low power environments
FPGA’s in Low Power Environments

Three Needs:

  • Monitor power consumption early in design process
  • Captures data-dependent transients and overall power consumption
  • Perform real-time constrain-driven automated power optimizations like the Area / Timing constraints are done today
jhdl tool suite
JHDL Tool Suite
  • JHDL Background
  • EDIF Import Parser
  • Cross Tool Naming and Correlation
jhdl background
JHDL Background
  • Create complex, high speed FPGA circuit modules programmatically from within Java.
  • Design Aids:
    • Digital circuit simulator
    • Circuit hierarchy browser
    • FPGA library primitives
    • Tools for exporting to EDIF and VHDL
jhdl lite
JHDL / LITE
  • Interoperation with existing commercial tool flows based on an HDL, through seemless JHDL-EDIF translation.
  • Single user interface
  • GUI event API developed
    • New tools to fully interact with JHDL
edif import parser
EDIF Import Parser
  • Development of new EDIF netlist tool
    • Developed independently from JDHL
    • Supports parsing of large EDIF netlists / merge multiple EDIF files
    • JHDL export feature added
  • EDIF Parser provides LITE tool suite
    • Capability to import 3rd party FPGA design
    • Provides consistent circuit database
cross tool naming correlation
Cross Tool Naming Correlation
  • Ability to correlate design resources between:
    • EDIF, JHDL, LITE, COTS PAR tool flow
  • Difficulty: Different vendor specific names and JHDL simulation interpret names
    • “Original” (Xilinx)
    • “Valid” (JHDL)
  • Added Name management resource
power visualization
Power Visualization
  • Tree-view of circuit and shows cumulative power consumption of each module in circuit
    • Sorted by power consumption
  • Plot of instantaneous power history of selected cells over time
    • Focuses on power modes / operating modes
    • Identify and characterize modes for different scenarios (Temporal view)
figure 4
Figure 4

modes

power

power visualization1
Power Visualization
  • Simulation uses capacitance values:
    • Post PAR via Xilinx’s XPower
    • Pre PAR via Power Modeling
      • A variety of modeling algorithms can be used
  • Simulator work with design during both Pre and Post PAR = more accurate modeling with a fully routed design
power analysis tools
Power Analysis Tools
  • XDL Importer
    • Detailed information of how a circuit was mapped, placed, and routed to be captured by JHDL environment
  • XPR Importer
    • Capture Xilinx’s XPower outputs
      • Post PAR circuit modeling
      • Create capacitance libraries of components and interconnect capacitance values
power analysis tools1
Power Analysis Tools
  • Two types of plots to visualize and verify power and architectural mapping correlations.
    • Interconnect Histogram
      • Number of each interconnect resources
        • Long Lines, Direct Connections, Double Lines, Hexagonal Lines, Programmable Interconnect Points
    • Net Characteristic Plot
      • Plot capacitance vs. net length, number of PIPs, or number of loads for every net in the diagram
power modeling
Power Modeling
  • Move power considerations to front of tool flow
    • Accurate models required to estimate and predict power consumption
  • Power Analysis tool:
    • Synthesized circuit compared to PAR
    • Allows development and experimentation of power models
      • Toggle rate only
      • Exact timing-level PAR circuit
power modeling1
Power Modeling
  • Lite exploits extensible JHDL data types
    • Representing hierarchical structure and connectivity of circuits of a FPGA
    • Data types augmented with load estimates for each net and cell
  • Dynamic power consumption
power modeling2
Power Modeling
  • Capacitance
    • FPGA logic resource
      • Published / extracted from Xpower reports
    • Interconnect route resource drives
      • Most difficult to model
      • Unknown until PAR
      • Fanout = strong predictor of net capacitance
        • 80% accuracy predicting where nets would be mapped
        • 3.2% mean power prediction error
        • 1.2% standard deviation
power optimization
Power Optimization
  • Specifically - Routing and interconnect power dissipation
    • 50-70% of FPGA dynamic power consumption is dissipated in clocking and interconnection network
    • Will not functionally alter user’s design
    • Future: EDIF Parser does provide API for synthesis level circuit mapping modifications which could be incorporated into power mapping API
power optimization1
Power Optimization
  • Allows user to combine COTS CAD tool constraints (timing and placement) with results from Power Analysis to meet designer’s needs.
clock table
Clock Table
  • Clock Table similar in appearance and capabilities but is tailored for clock analysis.
    • Toggle Rate
    • Number of sink flip-flops
    • Capacitance
    • Power consumption
power optimization algorithms
Power Optimization Algorithms
  • Slack minimization
    • Compares combinational logic delay of a net with its timing specification
    • Tightens the timing constraints on nets with the potential for long interconnects
  • Clock tree minimization
    • Place logic close to “trunk” of clock distribution tree
power optimization algorithms1
Power Optimization Algorithms
  • 2-terminal net co-location
    • Placing unity fanout signals tightly to use direct connects or internal slice routing
  • Area minimization
    • Balance clock tree paring with West - East signal routing (Virtex architecture)
results
Results (?)
  • Combine power optimization techniques
    • average dynamic power reduction 10.2%
    • peak reduction power reduction 19.4%
conclusion
Conclusion
  • Introduces LITE
    • Uses JHDL to address:
      • Power visualization
        • Power consumption logic level tree view
      • Power analysis
        • Interacts with COTS CAD tools
      • Power optimization algorithms
  • Elevate level of abstraction closer to design entry point