GPUs vs. FPGAs: What's the Difference?

Julio Franco

Posts: 9,116   +2,063
Staff member

Graphics processing units (GPUs) and field programmable gate arrays (FPGAs) are two of the three main processor types for imaging and other heavy calculations. Central processing units (CPUs) are the third type. Let's dig into the key differences between GPUs and FPGAs, their advantages, common use cases, and when to choose one over the other.

What is an FPGA?

An FPGA (field-programmable gate array) is an integrated circuit with a programmable hardware fabric that allows it to be reconfigured to behave like another circuit. Because its circuitry is not hard-etched, it can flexibly adapt to the needs of a specific machine learning algorithm. In the context of AI, this provides huge advantages in the ability of an FPGA to both support massively parallel workloads and boost the performance of a particular algorithm.

Choosing between GPUs and FPGAs

The main difference between GPUs and FPGAs is that GPUs were originally designed to render video and graphics. Their ability to handle workloads in parallel made them popular for deep learning applications for situations where the same workload needs to be performed many times at speed. For image recognition tasks, for example, GPUs are a natural choice.

FPGAs, on the other hand have the flexibility to be programmed to function as a GPU, ASIC, or other configurations. They can be programmed and optimized for specific algorithms, making them highly efficient in scenarios where general-purpose hardware might not be sufficient.

GPUs and the power of parallel processing

The greatest strength of GPUs is their ability to render graphics. From rendering high resolution images and animations to handling the complex calculations behind ray tracing, they are perfect for interfacing with displays and handling the computations needed to render scenes with high resolutions and detailed textures.

Editor's Note:
This guest blog post was written by the staff at Pure Storage, an US-based publicly traded tech company dedicated to enterprise all-flash data storage solutions. Pure Storage keeps a very active blog, this is one of their "Purely Educational" posts that we are reprinting here with their permission.

GPUs consist of multiple cores, each capable of executing thousands of mathematical operations simultaneously. This parallel architecture allows GPUs to tackle complex mathematical computations, such as matrix multiplications, Fourier transforms, and other linear algebra operations, much faster than CPUs.

GPUs are widely available on the market. From gaming to cryptomining to 3D modeling, consumers have no shortage of options to choose from. Unlike FPGAs, which often require specific configurations and can be challenging to program, many GPUs on the market come pre configured and ready to go. This user-friendly nature makes them accessible to a wide range of users and companies, ensuring they remain a popular choice in the tech industry.

FPGA advantages: Custom hardware acceleration

FPGAs are emerging as a powerful alternative to GPUs in the realm of artificial intelligence and high-performance computing. The biggest advantage of FPGAs is their programmability. Unlike GPUs which have a fixed design, FPGAs can be reprogrammed to implement custom logic and functionality. This programmability empowers developers to adapt the hardware to meet the specific requirements of their applications.

The ability to change the internal circuitry of FPGAs makes them an excellent choice for prototyping and development. Engineers can iterate quickly, testing different hardware configurations until they find the most efficient solution for their problem.

FPGAs often outshine GPUs in terms of latency and power usage, especially when fine-tuned for certain tasks. Developers can implement custom hardware accelerators tailored to specific tasks that may not be well-suited for the fixed architectures of GPUs. This allows FPGAs to offer a high degree of flexibility for fine-tuning hardware design to maximize efficiency. The caveat of course is graphics processing, where a high performance dedicated GPU will have better performance and power consumption.

Common use cases: FPGAs

Accelerating high-performance computing (HPCs)

Custom hardware acceleration means FPGAs are perfect for serving as programmable accelerators for inference in HPC clusters, which are great for training deep learning neural networks.

Real-time signal processing

FPGAs are very well-suited to applications that require low-latency and real-time signal processing, such as digital signal processing, radar systems, software-defined radios, and telecommunications.

Network optimization

FPGAs are ideal for offloading computationally intensive tasks, such as packet processing, encryption, and compression, from CPUs, reducing latency and increasing network throughput.

High-frequency trading

In trading, microseconds can be the difference between making millions of dollars and losing millions of dollars. High-frequency trading bots use FPGAs to implement custom algorithms that execute trades with minimum latency, providing a competitive advantage.

Aerospace and Defense applications

FPGAs are highly useful and beneficial in aerospace and defense systems, which use custom hardware accelerators for image and signal processing, encryption, and sensor data processing.

Common use cases: GPUs

In addition to gaming and rendering tasks, these are other typical GPU use cases:

Machine learning and deep learning

The popularity of artificial intelligence owes much to the exceptional processing power of GPUs. Training deep neural networks involves numerous matrix multiplications and activations, which GPUs handle with remarkable efficiency, significantly reducing training times.

Cryptocurrency mining

The mining of cryptocurrencies like Ethereum involves computationally intensive cryptographic operations, which GPUs can efficiently handle. For many years, GPU-based mining rigs dominated the scene, however, changes in mining difficulty, growing competition, and rising energy costs have reduced profit margins, so GPU mining is less popular than it used to.

Typical High-performance Computing applications

Scientific simulations, weather forecasting, and fluid dynamics simulations often require substantial computational power. GPUs provide the necessary horsepower to accelerate these simulations and improve time to results significantly.

Can You Use an FPGA as a GPU?

Yes, it's possible to use an FPGA as a GPU, but there are some important considerations and challenges involved. To use an FPGA as a GPU, you would need to design and implement a hardware architecture that emulates or replicates the functionality of a GPU. This requires significant expertise in FPGA design, as well as an in-depth understanding of GPU architecture and parallel processing techniques.

Also, keep in mind that while FPGAs can be highly efficient for specific tasks, they may not match the raw compute power and performance of modern GPUs, especially for graphics-intensive applications. FPGAs can also be power-hungry, and the power consumption of an FPGA-based GPU solution may not be as favorable as using dedicated GPUs.

Choosing between GPUs and FPGAs is an important decision that depends on the nature of the application, performance requirements, power constraints, and budget considerations. GPUs offer broad applicability and cost-effectiveness, making them a popular choice for many high-performance computing tasks. On the other hand, FPGAs provide a highly customizable and power-efficient solution for specific applications that demand hardware acceleration and real-time processing.

Permalink to story:

 
I would not be surprised to see AMD offering MI3XX FPGA implementation. It just make so much sense.
 
Why are the "GPUs" currently used in data centers for AI and HPC still called "GPUs" when they have nothing to do with graphics? They have no ROPs, no TMUs, no geometry units, or anything like that.
They are almost pure ALUs, and yes, with pure ALUs you can calculate graphics in a general way, but you can do it with a CPU too.
They should be called just Accelerators, regardless of their architecture or origin.
 
Last edited:
Professional Software Engineer speaking.

Some advice for you kids: If you go into an industry that does embedded work, do yourself a favor an learn how to program FPGAs. Trust me, you'll be *much* safer then if you are purely working Software.
 
CPUs: large instruction set and individual instruction pipelines for each core allows high versatility, especially when branching in code (if else), uses a lot of silicon for each core. High clock speeds allow for many instructions per second and higly optimized instructions such as avx and avx512 allow certain operations to be performed in few clock cycles.

GPUs: large number of compute cores being fed with instructions from a single instruction pipeline. These cores then perform this same instruction on each their own set of data, which is very fast for massively parallel workloads, such as image proccessing and convolutional networks. Additionally, the instruction set is smaller. The disadvantage is, that software with a lot of branching wastes clock cycles, since all cores in each group need to cycle evert branch, wasting time. This could really kill gpu performance a few generations back. But they are handling it better and better. High memory bandwidth allows the cores to be fed with data, but careful programming is required to not have the majority of the cores stalling while waiting for memory access.

FPGAs are programmable logic, the building elements of any application specific integrated circuit (ASIC), including cpus and gpus. Programming to these is done by describing hardware functionality, which then configures logic and lookup tables in any way possible. This allows the designer to create tailored processing pipelines allowing super fast flow processing of data and can perform operations massively in parallel in a single clock cycle. The tradeof is that such a pipeline is not very versatile. Also FPGAs tend to have low memory and a low memory bandwidth. They are clocked lower than cpus and gpus due to the larger paths that signals travel on chip. Often FPGAs are used to design and test functionality to then later be implemented in ASICs. Bitcoin mining is a popular example of this. Additionally, FPGAs can be fully reconfigured on the fly, allowing high versatility.
 
Last edited:
Back