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What is the Difference Between ARM and FPGA Processors?


ARM and FPGA are two very different types of processors used for a wide range of applications. Understanding the key differences between these architectures is important when selecting the right processor for a given application.

This article will provide an overview of ARM and FPGA processors, compare their architectures and performance attributes, analyze their programming approaches, and highlight suitable applications for each technology. Key differences will be summarized in tables throughout the article.

ARM Processors Overview

ARM processors are 32-bit and 64-bit RISC (Reduced Instruction Set Computer) CPUs that are designed for low cost and power efficiency. ARM cores are extremely popular in mobile and embedded devices due to their minimalist, power-optimized architecture.

Some key attributes of ARM processors:

  • RISC architecture with simpler instructions that execute in single clock cycles
  • Fixed hardware logic and execution pipelines
  • Excellent energy efficiency and low heat dissipation
  • Scalable performance from microcontrollers to application processors
  • Available as standardized cores licensed to many vendors
  • Requires software development in C/C++ or Assembly

ARM cores are used in billions of devices including smartphones, tablets, microcontrollers, and other embedded systems. Leading vendors like Qualcomm, Samsung, Nvidia, AMD, and Apple design their own ARM-based chips.

FPGA Processors Overview

FPGAs (Field Programmable Gate Arrays) are integrated circuits that can be programmed and reconfigured after manufacturing. This enables an FPGA to effectively morph into a custom computing device tailored for each application.

Key attributes of FPGAs:

  • Flexible fabric of logic blocks and routing that can be reconfigured
  • Parallel processing architecture optimized for data flow applications
  • Hardware level programmability using HDLs like Verilog or VHDL
  • High performance potential for parallel workloads
  • Well suited for DSP, ML, image processing, etc
  • Widely used for hardware acceleration and prototyping

While not as ubiquitous as ARM chips, FPGAs are popular for niche applications requiring custom hardware-level optimization and processing.

Architecture Comparison

ARM and FPGA processors have fundamental differences in their architecture and implementation:

ParameterARM ProcessorFPGA
Design PhilosophyRISC fixed architectureReconfigurable fabric
Processing ApproachSequential von NeumannParallel dataflow
Execution LogicFixed pipelines and data pathsReprogrammable logic blocks + routing
Hardware FlexibilityNone, fixed functionHighly flexible, customizable logic
Software FlexibilityHigh, can run different OS & appsLimited without HW changes
Performance AttributesPredictableApplication dependent
ProgrammingC/C++, AssemblyHDL (Verilog/VHDL)
Development ApproachSoftware algorithmsHardware logic synthesis

This table summarizes the key architectural differences between the two technologies:

RISC vs Reconfigurable Logic Architecture

The core design philosophy behind ARM and FPGA processors are completely different. The RISC architecture used in ARM chips has fixed hardware logic blocks tuned for efficiency in executing software instructions. In contrast, FPGAs contain a flexible fabric of logic blocks with programmable interconnects that can be rewired as needed.

Sequential vs Parallel Processing

ARM uses a classic sequential von Neumann architecture where instructions are executed one after another. FPGAs employ a dataflow architecture that processes data in parallel through customized pipelines. Multiple operations can occur simultaneously.

Fixed Pipelines vs Reconfigurable Logic

ARM processors rely on hardwired logic blocks and execution pipelines tailored for RISC instructions. With FPGAs, any hardware function can be synthesized using the basic logic elements, letting you customize data paths and control logic.

Software vs Hardware Flexibility

ARM processors are software-flexible – different operating systems and applications can run on the same ARM core. FPGAs are the opposite – they are hardware-flexible and must be physically reprogrammed for new functions, but software is largely fixed.

This contrast in fundamental architecture leads to major differences in performance, programming, and use cases.

Performance Comparison

Both ARM and FPGA offer excellent performance, but in very different ways:

Performance AttributeARM ProcessorFPGA
Processing StyleSequentialParallel
Clock SpeedsUp to ~3 GHzTypically 100-400 MHz
Latency10s – 100s of cyclesSingle cycle throughput
ThroughputGigabytes/secTerabytes/sec potential
Performance ScaleUp to multicore CPUs10X-100X speedups possible
Power EfficiencyExcellentConfigurable for efficiency
Cost EfficiencyLow cost per unitHigh development costs

Let’s analyze the key performance differences:

Sequential vs Parallel Execution

The von Neumann nature of ARM processors means they execute operations sequentially, albeit with some instruction parallelism via pipelines. FPGAs process data simultaneously in customized parallel pipelines, enabling much higher throughput. However, latency is lower on ARM cores.

Clock Speed Differences

ARM cores reach clock speeds up to around 3 GHz today by optimizing critical paths for fast sequential execution. FPGAs typically run at 100-400 MHz but make up for lower clocks through massive parallelism.

Throughput and Latency

ARM processors can complete single operations faster due to higher clocks (latency in 10s-100s of cycles). However, FPGA throughput for highly parallel tasks like encryption or image processing can be orders of magnitude higher (terabytes/sec).

Performance Scalability

ARM scales well to multicore CPUs with shared memory access. FPGAs can provide 10X-100X speedups for parallel workloads by customizing logic, but single thread performance lags.

Power and Cost Efficiency

ARM excels at power efficiency for mobile devices with clock gating and power management features. FPGAs can also be tuned for power efficiency but higher performance comes at a cost premium, while ARM chips leverage economies of scale.

For the right applications, FPGAs can significantly outperform ARM processors. But ARM remains superior for general purpose computing and single-threaded tasks.

Programming Model Comparison

ARM and FPGAs have completely different programming methodologies:

Programming AttributeARMFPGA
Primary LanguagesC/C++, AssemblyVerilog, VHDL (HDLs)
Abstraction LevelSoftware algorithmsHardware logic
Device LearningNot requiredMust learn FPGA fabric
Programming ApproachProcedural, sequentialConcurrent, parallel
DebuggingSoftware debuggingHardware verification
OptimizationCompiler optimizationsLogic synthesis optimization

Some key aspects:

Software vs Hardware Languages

ARM processors are programmed using software languages like C/C++ and Assembly to implement algorithms. FPGAs require hardware description languages (HDLs) like Verilog and VHDL that describe digital logic gates and connections.

Abstraction from Hardware

Software programmers can develop code without knowledge of the underlying processor. With FPGAs, you must understand the low-level fabric in order to synthesize logic that maps efficiently.

Programming Paradigm

ARM code is written procedurally with sequential instructions. FPGA logic must be designed concurrently with parallel data flows in mind. Different mental models are required.

Debugging and Optimization

Software debugging tools are more mature. FPGA optimization relies heavily on the synthesis tool mapping designs to the underlying hardware as efficiently as possible.

FPGA programming has a much steeper learning curve but enables hardware-level customization. ARM programming is more accessible thanks to abundant software resources.

Use Case Comparison

Given their differing attributes, ARM and FPGAs are suited for very different applications:

Use CasesARM ProcessorsFPGAs
Mobile devicesExcellent fitNot suitable
Embedded systemsWidely usedOverkill for most
IoT endpointsWell suitedPremium use cases
Cloud accelerationLimited suitabilityExcellent fit
DSP algorithmsCapable for many appsHigher performance possible
Computer visionOften sufficientMore demanding apps benefit
Autonomous vehiclesGenerally not usedCritical for some subsystems

Here are some typical use cases that favor ARM or FPGAs:

Mobile Devices

ARM processors are designed for mobile applications where low power draw is critical. FPGAs are overkill for smartphones and tablets due to cost and power constraints.

Embedded Systems

ARM MCUs and application processors power most embedded electronics like home appliances, sensors, industrial, etc. FPGAs are usually too expensive for mainstream embedded use.

IoT Endpoints

ARM Cortex M class MCUs feature in most IoT endpoint designs. Some higher performance IoT applications utilize FPGAs where ML acceleration is required locally.

Cloud Acceleration

FPGAs are widely used to accelerate computationally intensive tasks in data centers by customizing parallel pipelines. ARM servers have limited suitability currently.

Computer Vision

Lower resolution computer vision runs well on ARM chips. But FPGA acceleration becomes important for higher resolution or when deep learning algorithms are used.

Autonomous Vehicles

ARM processors typically do not have the performance for autonomous vehicle subsystems. FPGAs are critical for sensor fusion, perception, and decision making.

For any given application, the tradeoffs between these technologies must be carefully evaluated when selecting a processing platform.


ARM and FPGA processors have fundamental differences in architecture, programming, performance attributes, and typical applications.

Key Takeaways:

  • ARM processors feature a RISC architecture optimized for low cost and power efficiency. FPGAs provide a flexible fabric of logic blocks that can be reconfigured.
  • ARM uses a sequential von Neumann architecture while FPGAs leverage parallel dataflow processing.
  • FPGAs can accelerate suitable parallel workloads by 10X-100X but have a steep development curve. ARM offers broadly accessible software-based programming.
  • ARM excels in mobile and embedded devices. FPGAs are used where custom hardware acceleration is critical.

Understanding these complementary technologies is important when architecting systems. With their respective strengths, ARM and FPGAs will continue powering many of the world’s electronic devices into the foreseeable future.

Frequently Asked Questions

What are the key differences between ARM and FPGA architectures?

ARM uses fixed RISC processor cores while FPGAs provide reconfigurable logic fabrics. ARM has a sequential von Neumann architecture whereas FPGAs use a parallel dataflow architecture.

When is ARM processors the best choice over FPGA?

ARM processors are superior for mobile applications, embedded systems, and general purpose computing where low cost and power efficiency are critical. Their software programmability is also more accessible.

When is FPGA the right choice over ARM processors?

FPGAs are chosen for applications requiring custom hardware acceleration and parallel processing. They excel in cloud acceleration, high performance DSP and computer vision algorithms, and critical autonomy systems.

Can ARM processors be reconfigured like FPGAs?

No, ARM processors have fixed architecture and cannot be reconfigured at the hardware level. FPGAs can be reprogrammed even after manufacturing to morph into customized accelerators.

Do FPGAs completely replace ARM processors?

No, FPGAs complement rather than replace ARM processors in most systems. ARM CPUs are still used to execute control, I/O and application layer software alongside FPGA acceleration. The technologies have different strengths.




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