Tech is always evolving and introducing innovations regularly. One of the recent advancements is NPUs, which have swiftly become a hot topic in the tech community. It’s crucial to understand that not all NPUs are the same. Some are better than others, so it’s essential to learn how NPU performance is evaluated.

An NPU, or Neural Processing Unit, is a specialized hardware designed to accelerate artificial intelligence (AI) tasks, particularly in devices like smartphones and tablets. As we increasingly rely on these devices for handling complex tasks, the performance of their NPUs can significantly impact our user experience.

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The Role of NPUs in SoCs/Processors

NPUs are used in Systems on a Chip (SoCs) and other microprocessors. The SoC is the brain of a smartphone or computer. It is made up of different components such as the CPU cores, GPU, memory, modems, and these days, NPUs.

The addition of NPUs to SoCs has made smartphones and other computers a lot more intelligent. This is because NPUs are good at doing tasks that require a lot of thinking. Such tasks include recognizing faces, understanding words, translating language, analyzing images, etc.

Even though the CPU cores on some SoCs can do these tasks, they’re poor at it and can use up a lot of battery and time. NPUs on the other hand can do these tasks quickly and efficiently, saving battery and time. This frees up the CPU cores (and GPU) to tackle other tasks such as gaming for example.

The teamwork between the NPU and the rest of the SoC makes our devices more intelligent and helps them work better.

NPU performance

Evaluating NPU Performance

Evaluating NPU performance is a complex task that involves many factors and metrics. 

Factors that influence NPU performance

1. Design and Architecture

The design and organization of an NPU’s architecture play a large part in how well it performs. These include the number and type of computing cores, memory, instruction set, etc. Different types of AI workloads may benefit or suffer from different architectures.

2. Fabrication process

The process node refers to the size of the transistors and the technology that is used to build the NPU. Smaller process nodes are better because they enable higher clock speeds, use less battery, and are more powerful.

3. The Neural Network

The neural network (see: NPU vs TPU) that the NPU is working on plays a huge part in its performance. Different neural networks may have different computational and memory requirements, and may also have different levels of compatibility and efficiency with different NPUs.

4. Software

The NPU software also plays a part in how well the NPU performs. Good software will bring out the best in the NPU whilst bad software will reduce its effective performance. NPU software includes the tools and libraries that enable the development, deployment, and optimization of AI applications on the NPU.

Metric for measuring NPU performance

There is no single or standard way to measure the performance of an NPU. Thus different metrics are used to capture different aspects of an NPU’s abilities and limitations. Some of the common metrics used to measure NPU performance are:

TOPS

TOPS (Tera Operations Per Second) measures how fast an NPU works. It calculates the theoretical peak performance by looking at the number of operations that an NPU can do in one second. You find TOPS by multiplying the number of MAC units, the speed it works at, and a special factor of 2. For example, if an NPU has 54,000 MAC units and works at 1GHz, it can achieve 108 TOPS.

TOPS per Watt (TOPS/W)

TOPS/W (Tera Operations Per Second per Watt) measures the power efficiency of the NPU in terms of the number of operations that the NPU can execute in a second per unit of power consumption. Dividing the TOPS by the power consumption of the NPU (usually in watts) is how to calculate TOPS/W.  For example, an NPU that can achieve 108 TOPS with 10W of power consumption can achieve 10.8 TOPS/W.

Throughput (or latency)

Throughput (or latency), measures the actual performance of the NPU in terms of the number of inputs (usually images or frames) that the NPU can process per second.

Accuracy (or Error rate)

Accuracy (or error rate) measures the quality or correctness of the results produced by the NPU. This refers to the percentage of inputs that the NPU can correctly classify or predict (or the percentage of inputs that the NPU can incorrectly classify or predict).

NPU Benchmarks

Various benchmarks can measure NPU performance. These benchmarks run a series of tests that evaluate how well the NPU performs under different conditions. Some of these benchmarks include AI Benchmark, MLPerf, and Antutu.

NPU performance

The importance of NPU performance in overall SoC performance

The NPU’s performance is a crucial factor in how well the whole system-on-chip (SoC) works. NPU performance affects the SoC in three main ways:

  1. Functionality: This is about what smart things the SoC can do, like recognizing images, understanding language, or making speech. It depends on how the NPU is built and how it works with other parts of the SoC.
  2. Efficiency: This is how well the SoC uses its resources to get things done – how fast, accurate, and power-friendly it is. It relies on NPU factors like TOPS (operations per second), power efficiency, and how well it works with the rest of the SoC.
  3. Scalability: This is about how easily the SoC can handle different needs or changes, like adjusting to new tasks or environments. It depends on how flexible and adaptable the NPU is, and how well it fits with the other parts of the SoC.

The NPU’s performance is becoming more important as our devices do more smart tasks. It directly impacts how well the device works and how users experience it.

Comparing NPU Performances

When comparing the performance of different NPUs, several factors come into play. These include the:

  • architecture,
  • number of cores,
  • neural network,
  • processing speed,
  • power efficiency,
  • size, and
  • integration with other components of the SoC. 

Tera Operations Per Second (TOPS) measures the processing speed, while power efficiency measures how much power the NPU uses while performing its tasks.

 The size of the NPU can also impact its performance, with smaller NPUs fitting into smaller devices but potentially offering less performance than larger ones. Finally, how well the NPU integrates with other components of the SoC can also impact its performance.

Conclusion

In this blog post, we explored the vital role of Neural Processing Units (NPUs) on SoCs and other processors. NPUs are specialized circuits for AI tasks that are essential in today’s technology.

We also covered how NPUs fit into SoC architectures, enhancing overall device performance and efficiency by working with other components. Then we touched on factors influencing NPU performance and how it’s measured.

Understanding NPU performance is not just for tech pros – anyone curious about their device’s inner workings should grasp it. As AI becomes more integrated into our daily lives, NPUs become increasingly important.

We hope this post has piqued your interest in NPUs and SoC components. Keep exploring, keep learning, and stay tuned for more insights into the tech world!

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