Comparison of resource consumption of different design methods in FPGA design

ampheoampheo
4 min read

Table of contents

FPGA designs can be implemented using various methodologies, each with different impacts on logic resources (LUTs, FFs), memory (BRAM), DSP slices, and power consumption. Below is a detailed comparison of common design approaches.

1. Design Methodologies Compared

MethodDescriptionBest For
Hardware Description Language (HDL)Directly describes logic in Verilog/VHDL. Most control over optimization.High-performance, low-latency designs
High-Level Synthesis (HLS)Uses C/C++/Python (e.g., Xilinx Vitis HLS). Automatically generates HDL.Algorithmic designs, rapid prototyping
IP Core IntegrationPre-built blocks (e.g., Xilinx IP, Intel Megafunctions). Optimized for specific tasks.Standard functions (FFT, Ethernet)
Graphical Design (Block Diagrams)Drag-and-drop logic (e.g., Xilinx Vivado Block Design).Simple systems, education
Soft Processors (e.g., MicroBlaze/Nios II)FPGA-implemented CPUs running compiled C code.Control-heavy tasks

2. Resource Consumption Comparison

A. Logic Elements (LUTs/FFs)

MethodLUT UsageFF UsageNotes
Handwritten HDLLowestLowestManual optimization reduces overhead.
HLSModerate to HighModerateExtra logic for control FSM.
IP CoresLow to ModerateLowPre-optimized but fixed functionality.
Block DiagramsHighHighGUI abstraction adds overhead.
Soft ProcessorsVery HighVery HighCPU infrastructure consumes resources.

B. Memory (BRAM)

MethodBRAM UsageNotes
Handwritten HDLLow (manual control)Explicit inference of BRAM.
HLSModerate to HighAutomatic memory partitioning.
IP CoresDepends on IPFIFOs, buffers consume BRAM.
Soft ProcessorsHighInstruction/data caches use BRAM.

C. DSP Slices

MethodDSP UsageNotes
Handwritten HDLOptimizedDirect instantiation of DSP48E1.
HLSHighAuto-inference may overuse DSPs.
IP CoresOptimizedMath-heavy IP (FFT, FIR) use DSPs.
Soft ProcessorsLowDSPs unused unless explicitly coded.

D. Power Consumption

MethodDynamic PowerStatic Power
Handwritten HDLLowestDepends on design
HLSModerateHigher due to FSM
IP CoresLow to ModerateFixed for IP
Soft ProcessorsHighCPU logic is power-hungry

3. Latency & Performance

MethodClock FrequencyPipeline Efficiency
Handwritten HDLHighestFully customizable
HLSModerateDepends on directives
IP CoresHighPre-optimized
Soft ProcessorsLow (50-200 MHz)Limited by CPU arch.

4. Development Time vs. Efficiency Tradeoff

MethodDevelopment SpeedResource Efficiency
Handwritten HDLSlowestHighest
HLSFastModerate
IP CoresFastestHigh (for targeted use)
Soft ProcessorsFast (C code)Lowest

5. When to Use Each Method?

ScenarioRecommended Method
Ultra-low-latencyHandwritten HDL
Algorithm accelerationHLS (with pragmas)
Standard protocolsIP cores (Ethernet, PCIe)
Control logicSoft processors
Education/PrototypingBlock diagrams

6. Optimization Tips

  1. For HDL Designs:

    • Use FSM encoding (one_hot vs binary) to save LUTs.

    • Manually instantiate DSP48E1 for math operations.

  2. For HLS:

    • Apply #pragma PIPELINE to reduce latency.

    • Use #pragma ARRAY_PARTITION to optimize BRAM.

  3. For IP Cores:

    • Adjust parameters (e.g., FIFO depth) to minimize BRAM.

  4. For Soft Processors:

    • Disable unused peripherals to save logic.

7. Real-World Example: FIR Filter Implementation

MethodLUTsDSPsFmax (MHz)
Handwritten HDL1508400
HLS (Vitis)2208350
Xilinx FIR IP Core10010500

Conclusion

  • Highest Efficiency: Handwritten HDL (best for LUT/FF/DSP optimization).

  • Fastest Development: HLS or IP cores (trade resource efficiency for speed).

  • Worst Efficiency: Soft processors (use only for control-heavy tasks).

0
Subscribe to my newsletter

Read articles from ampheo directly inside your inbox. Subscribe to the newsletter, and don't miss out.

resource consumptionfpgaDSP

Written by

ampheo
ampheo