Quartus® Prime Pro Edition User Guide: Power Analysis and Optimization

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ID 683174
Date 4/01/2024
Public
Document Table of Contents
Document Table of Contents x
Answers to Top FAQs 1. Power Analysis 2. Power Optimization 3. Power Analysis and Optimization Document Archive A. Quartus® Prime Pro Edition User Guides
1. Power Analysis x
1.1. Power Analysis Tools 1.2. Running the Power Analyzer 1.3. Specifying Power Analyzer Input 1.4. Viewing Power Analysis Reports 1.5. Power Analysis in Modular Design Flows 1.6. Scripting Support 1.7. Power Analysis Revision History
1.3. Specifying Power Analyzer Input x
1.3.1. Settings for Power Analysis 1.3.2. Specifying Signal Activity Data 1.3.3. Specifying the Default Toggle Rate 1.3.4. Specifying Toggle Rates for Specific Nodes 1.3.5. Avoiding Simulation Node Name Match
1.3.2. Specifying Signal Activity Data x
1.3.2.1. Using Simulation Signal Activity Data in Power Analysis 1.3.2.2. Signal Activities from RTL (Functional) Simulation, Supplemented by Vectorless Estimation 1.3.2.3. Signal Activities from Vectorless Estimation and User-Supplied Input Pin Activities 1.3.2.4. Signal Activities from User Defaults Only
1.3.2.1. Using Simulation Signal Activity Data in Power Analysis x
1.3.2.1.1. Generating Signal Activity Data for Power Analysis 1.3.2.1.2. Generating Standard Delay Output for Power Analysis 1.3.2.1.3. Simulation Glitch Filtering
1.3.2.2. Signal Activities from RTL (Functional) Simulation, Supplemented by Vectorless Estimation x
1.3.2.2.1. RTL Simulation Limitation
1.3.4. Specifying Toggle Rates for Specific Nodes x
1.3.4.1. Clock Node Toggle Rates
1.5. Power Analysis in Modular Design Flows x
1.5.1. Complete Design Simulation Power Analysis Flow 1.5.2. Modular Design Simulation Power Analysis Flow 1.5.3. Multiple Simulation Power Analysis Flow 1.5.4. Overlapping Simulation Power Analysis Flow 1.5.5. Partial Design Simulation Power Analysis Flow 1.5.6. Vectorless Estimation Power Analysis Flow
1.5.5. Partial Design Simulation Power Analysis Flow x
1.5.5.1. Specifying Start and End Time for Signal Activity Calculations
1.6. Scripting Support x
1.6.1. Running the Power Analyzer from the Command–Line
2. Power Optimization x
2.1. Factors Affecting Power Consumption 2.2. Design Space Explorer II for Power-Driven Optimization 2.3. Power-Driven Compilation 2.4. Design Guidelines 2.5. Power Optimization Advisor 2.6. Power Optimization Revision History
2.1. Factors Affecting Power Consumption x
2.1.1. Design Activity and Power Analysis 2.1.2. Device Selection 2.1.3. Environmental Conditions 2.1.4. Device Resource Usage 2.1.5. Signal Activity
2.1.4. Device Resource Usage x
2.1.4.1. Number, Type, and Loading of I/O Pins 2.1.4.2. Number and Type of Hard Logic Blocks 2.1.4.3. Number and Type of Global Signals
2.1.5. Signal Activity x
2.1.5.1. Toggle Rate 2.1.5.2. Static Probability
2.3. Power-Driven Compilation x
2.3.1. Power-Driven Synthesis 2.3.2. Power-Driven Fitter 2.3.3. Area-Driven Synthesis 2.3.4. Gate-Level Register Retiming 2.3.5. Quartus® Prime Compiler Settings 2.3.6. Assignment Editor Options
2.3.1. Power-Driven Synthesis x
2.3.1.1. Memory Block Optimization 2.3.1.2. Power-Aware Logic Mapping 2.3.1.3. Power-Aware Memory Balancing
2.4. Design Guidelines x
2.4.1. Clock Power Management 2.4.2. Pipelining and Retiming 2.4.3. Architectural Optimization 2.4.4. I/O Power Guidelines 2.4.5. Dynamically Controlled On-Chip Terminations (OCT) 2.4.6. Memory Optimization (M20K/MLAB) 2.4.7. DDR Memory Controller Settings 2.4.8. DSP Implementation 2.4.9. Reducing High-Speed Tile (HST) Usage 2.4.10. Unused Transceiver Channels 2.4.11. Periphery Power reduction XCVR Settings
2.4.1. Clock Power Management x
2.4.1.1. Clock Gating 2.4.1.2. Clock Enable in Memory Blocks 2.4.1.3. LAB Clock Power 2.4.1.4. Clock Enables 2.4.1.5. Global Signals 2.4.1.6. Merge Clocks
2.4.1.1. Clock Gating x
2.4.1.1.1. Root Clock Gate 2.4.1.1.2. Sector Clock Gate 2.4.1.1.3. I/O PLL Clock Gate
2.4.1.3. LAB Clock Power x
2.4.1.3.1. LAB-Wide Clock Enable Example
2.4.1.5. Global Signals x
2.4.1.5.1. Viewing Clock Details in the Chip Planner
2.4.6. Memory Optimization (M20K/MLAB) x
2.4.6.1. Implementation 2.4.6.2. Rd/Wr Enables
2.4.11. Periphery Power reduction XCVR Settings x
2.4.11.1. Transceiver Settings 2.4.11.2. I/O Current Strength
2.5. Power Optimization Advisor x
2.5.1. Set Realistic Timing Constraints 2.5.2. Appropriate Device Family 2.5.3. Dynamic Power 2.5.4. Static Power 2.5.5. Appropriate I/O Standards 2.5.6. Use RAM Blocks 2.5.7. Shut Down RAM Blocks 2.5.8. Clock Enables on Logic 2.5.9. Pipeline Logic to Reduce Glitching
2.5.1. Set Realistic Timing Constraints x
2.5.1.1. Find Timing Information
Answers to Top FAQs
1. Power Analysis
2. Power Optimization
3. Power Analysis and Optimization Document Archive
A. Quartus® Prime Pro Edition User Guides

2.4.2. Pipelining and Retiming

Glitches are unnecessary and unpredictable temporary logic switches at the output of combinational logic. Designs with glitches consume more power, because of faster switching activity. A glitch usually occurs when there is a mismatch in input signal timing, leading to unequal propagation delay.

For example, consider a 2-input XOR gate where one input changes from 1 to 0, and moments later the other input changes from 0 to 1. For a short time, both inputs become 1 (high), resulting in 0 (low) at the output of the XOR gate. Then, when the second input transition takes place, the XOR gate output becomes 1 (high). Therefore, before the output becomes stable, the input delay produces a glitch in the output.

Figure 34. XOR Gate Showing Glitch at the Output

A glitch can propagate to subsequent logic and create unnecessary switching activity, increasing power consumption. Circuits with many XOR functions, such as arithmetic circuits or cyclic redundancy check (CRC) circuits, tend to have many glitches if there are several levels of combinational logic between registers.

Registers stop glitches from propagating through combinational paths. Pipelining is a technique that breaks combinational paths by inserting registers. By reducing logic-level numbers between registers, pipelining can result in higher clock speed operations. However, pipelining increases the latency of a circuit in terms of the number of clock cycles to a first result.

The following figure shows how pipelining breaks a long combinational path.

Figure 35. Pipelining Example

This reduction in switching activity lowers power dissipation in combinational logic. However, for designs with few glitches, pipelining can increase power consumption by adding unnecessary registers. Pipelining can also increase resource utilization.

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