Stepping into RISC-V: A Detailed Look at Four Common RISC-V CPU Development Boards

In the contemporary realm of technology, open-source has emerged as a prevailing paradigm. This trend extends beyond the software sector, infiltrating the hardware domain, particularly within the sphere of microprocessor design. RISC-V, an open-source Instruction Set Architecture (ISA), has garnered extensive global attention and application. As physical embodiments of the RISC-V architecture, RISC-V CPU development boards have become instrumental tools for a multitude of developers and corporations.

The significance of RISC-V CPU development boards lies in their provision of a cost-effective, efficient, and adaptable avenue for the development and testing of RISC-V-based applications. These boards find broad applicability across a myriad of sectors, encompassing but not limited to the Internet of Things (IoT), Artificial Intelligence (AI), embedded systems, and network devices. With the continuous maturation and expansion of the RISC-V ecosystem, the application scope of RISC-V CPU boards is also correspondingly broadening.

The objective of this discourse is to delve into the intricacies of RISC-V and four representative RISC-V CPU development boards, encompassing their technical specifications, advantages, and application scenarios. Through an in-depth exploration of these boards, we aim to provide a comprehensive reference resource for professional makers, thereby enabling them to make more informed decisions when selecting and utilizing RISC-V CPU boards.

What is RISC-V?

RISC-V was initially proposed in 2010 by computer science researchers at the University of California, Berkeley. The design principles of RISC-V are simplicity, openness, and modularity with the aim of creating a universally applicable computer Instruction Set Architecture that can be freely used, extended, and customized. Since its inception, RISC-V has found widespread application globally and has attracted substantial participation from developers and corporations.

Foundational Architecture and Design Principles of RISC-V

The foundational architecture of RISC-V is based on the Reduced Instruction Set Computing (RISC) principle, implying its utilization of a set of simple yet efficient instructions, rather than a complex and variable instruction set. The design principles of RISC-V are modularity and extensibility, indicating that developers can select the instruction set modules they require, and even add custom instructions, according to their needs.

Advantages and Challenges of RISC-V

The primary advantages of RISC-V lie in its openness and flexibility. As an open-source Instruction Set Architecture, RISC-V offers developers an unprecedented level of freedom, enabling them to customize processors according to their needs. Furthermore, the modular design of RISC-V endows it with high flexibility and extensibility.

Nevertheless, RISC-V also faces a few challenges. Firstly, being a relatively new architecture, it might not yet have sufficient hardware and software support in certain application domains. Secondly, while the openness of RISC-V provides developers with considerable freedom, it also implies that developers need to invest more time and resources in customizing and optimizing their solutions.

Popular RISC-V CPU development boards

1. HiFive Unmatched

HiFive Unmatched is a Linux-running RISC-V development board meticulously crafted by SiFive. It can be seen as an early design of a development-oriented Linux PC based on a RISC-V processor.

Developers can use HiFive Unmatched to create the RISC-V based software they need for the RISC-V platform - from real-time operating systems to custom Linux distributions, as well as compilers, libraries, and applications that accompany product design. Additionally, HiFive Unmatched can be used to natively test and build RISC-V code.

Figure: HiFive Unmatched development board

This development board is powered by SiFive Freedom U740 (FU740), which includes a high-performance multicore, 64-bit dual-issue, superscalar RISC-V processor (SiFive Essential™ U74-MC). It's equipped with 16GB DDR4 memory, gigabit Ethernet, PCIe expansion slots, USB 3 interface, as well as M.2 slots for Wi-Fi, Bluetooth, and NVMe storage. Additionally, there's a fifth core (SiFive Essential S71 monitor core) for real-time applications. SiFive's Mix+Match technology offers a powerful combination of applications and real-time processing. The S71 (RV64IMAC) core can handle auxiliary functions and work in tandem with the U74-MC cluster, making it an ideal heterogeneous software development platform where Linux and real-time operating systems can coexist.

Therefore, developers can use HiFive Unmatched to create the RISC-V based software they need for the RISC-V platform - from real-time operating systems to custom Linux distributions, as well as compilers, libraries, and applications that accompany product design. Additionally, HiFive Unmatched can be used to natively test and build RISC-V code.

The main features of HiFive Unmatched are as follows:

• Powerful Performance: The SiFive Unleashed features an optimized 5-core CPU design with a clock speed of up to 1.5GHz, making it capable of handling various high-load tasks with ease. Whether it's processing large amounts of data, running complex algorithms, or providing graphic rendering, it shows excellent performance.
• High Customizability: The biggest highlight of the SiFive Unleashed is its customizability. Developers can customize the CPU to best suit their applications using SiFive's toolchain and development environment. This allows developers to deeply explore the potential of the processor and create unique products.
• High Flexibility: SiFive Unleashed not only excels in performance and customization, but also has high flexibility. It supports various memory interfaces, storage devices, and communication interfaces, allowing developers to flexibly configure according to specific application requirements.
• Mature Ecosystem: SiFive actively promotes the construction of the RISC-V ecosystem and has built a complete development environment with many partners. This means developers can get rich software support and development tools on SiFive Unleashed, thus simplifying the development process and improving development efficiency.

2. VisionFive 2

SiFive Technology recently launched VisionFive 2, the world's first high-performance RISC-V single-board computer integrated with a 3D GPU. It provides developers with a powerful platform to create and test RISC-V based software, from real-time operating systems to customized Linux distributions, as well as compilers, libraries, and applications that accompany product design.

Figure: VisionFive 2 development board

VisionFive 2 is driven by the JH7110 multimedia processor, a quad-core 64-bit SoC running at up to 1.5 GHz, offering powerful computing capabilities. It also integrates IMG BXE-4-32, supporting OpenCL 3.0, OpenGL ES 3.2, and Vulkan 1.2, which means VisionFive 2 also performs excellently in graphics processing.

VisionFive 2 is equipped with a comprehensive range of audio and video interfaces, including DVP, MIPI, HDMI, and stereo audio interfaces, providing strong support for multimedia applications. In addition, it also features two network interfaces and a 40-pin full-function GPIO, making it compatible with universal peripheral modules of various mainstream development boards.

In terms of expandability, VisionFive 2 provides expansion interfaces for peripherals such as PCIE, USB, SDIO, as well as M.2 connectors, eMMC sockets, USB 3.0 ports, TF card slots, and other rich I/O peripherals, offering users a wide range of expansion choices.

Software compatibility is another major advantage of VisionFive 2. Not only does it support Huawei's HarmonyOS, but it also supports various operating systems such as Debian, providing users with a wide range of software choices.

The main features of VisionFive 2 are as follows:

• Powerful Performance: VisionFive 2 is equipped with the JH7110 multimedia processor, offering powerful computing capabilities. It also integrates IMG BXE-4-32, supporting OpenCL 3.0, OpenGL ES 3.2, and Vulkan 1.2, performing excellently in graphics processing.
• Rich Interfaces: VisionFive 2 comes with a comprehensive range of audio and video interfaces, including DVP, MIPI, HDMI, and stereo audio interfaces. It also features two network interfaces and a 40-pin full-function GPIO, making it compatible with universal peripheral modules of various mainstream development boards.
• High Expandability: VisionFive 2 provides expansion interfaces for peripherals such as PCIE, USB, SDIO, as well as M.2 connectors, eMMC sockets, USB 3.0 ports, TF card slots, and other rich I/O peripherals.
• Broad Software Compatibility: In addition to supporting OpenCL 3.0, OpenGL ES 3.2, and Vulkan 1.2, VisionFive 2 not only supports Huawei's HarmonyOS but also supports various operating systems such as Debian.

3. BeagleV-Ahead

On July 14th, StarFive partnered with BeagleBoard, a top global open-source hardware development community, to launch the first single-board computer based on RISC-V, the BeagleV-Ahead. This single-board computer is equipped with StarFive's high-performance mass-produced RISC-V prototype chip, VisionFive 1520. Developers can run multiple operating systems such as Android, Yocto, and Ubuntu on the BeagleV-Ahead single-board computer, exploring innovative applications of RISC-V in fields such as AI, IoT, and robotics.

Figure: BeagleV-Ahead

BeagleV-Ahead is akin to a minimalist computer, capable of performing basic functions such as computation, storage, and input/output, and can be directly embedded into smart products for use. It has a built-in 4-core Xuantie C910, as well as DSP, GPU, NPU, and other processors, achieving computational acceleration through multi-core heterogeneity. At the same time, it supports 64-bit LPDDR4X and is equipped with a wealth of IO resources to meet the needs of flexible expansion.

The main control chip of BeagleV-Ahead is StarFive's TH1520 SoC, which showcases the high performance, low power consumption, and high security features of StarFive's Xuantie RISC-V processor. It can perform tasks such as multimodal perception, 4K video processing, and Int8 AI computation. More importantly, BeagleV-Ahead is extremely developer-friendly. It can be used simply by connecting a USB, significantly lowering the barrier to RISC-V development. Based on the full-stack optimized ecosystem and platform capabilities provided by StarFive, BeagleV-Ahead can natively support mainstream operating systems such as Android, Linux, Yocto, Ubuntu, and Fedora. This breaks down the barriers between RISC-V innovation research and development and market implementation, helping developers' ideas to accelerate incubation and implementation.

Figure: BeagleV-Ahead

The main features of BeagleV-Ahead are as follows:

• Portable size: It's very compact, a pocket-sized board.
• High-performance processor: Equipped with T-Head TH1520 (Quad-core Xuantie C910 processor), running at speeds up to 2GHz, it has outstanding computational performance.
• High-speed memory and storage: Comes with 4GB LPDDR4 memory and a 16GB flash card, providing ample operating and storage space.
• Rich interfaces: The TH1520 provides a wealth of interfaces, and the BeagleV-Ahead board basically brings out all the interfaces.

4. D1-H Development board —— Nezha

Allwinner Technology has launched its first chip based on the RISC-V instruction set, the D1, which is a high-performance chip integrated with Alibaba's T-Head 64-bit C906 core. It supports RVV, has a main frequency of up to 1GHz, and can run a variety of systems such as Linux and RTOS. The powerful features of the D1 chip include support for up to 4K H.265/H.264 decoding, an integrated HiFi4 DSP, and the ability to connect up to 2GB DDR3 externally. This makes the D1 chip widely applicable in various fields such as smart cities, smart cars, smart commercial displays, smart home appliances, smart offices, and scientific research and education.

For the D1 chip, Allwinner has launched a dedicated development board, codenamed "Nezha". This development board is the world's first mass-produced development board that supports the 64-bit RISC-V instruction set and Linux system, marking the entry of AIoT development into a new era. The Nezha development board is not designed to carry heavy computing applications, but is specifically designed for the RV64 open-source community and IoT applications. It operates at temperatures below 50°C, and the chip's power consumption is less than 0.1A@5V, so it can run easily without a heatsink.

Figure: D1-H Nezha Development Board

The D1-H Development Board—Nezha is equipped with most of the peripherals needed for IoT applications, including MIPI LCD, HDMI, USB, and ETH, as well as interfaces like SPI/UART/IIC/PWM/LEDC/IS/GPIOs. This allows developers to easily and quickly build projects. The emergence of this development board will provide strong support for the development and implementation in various fields such as smart cities, smart cars, smart commercial displays, smart home appliances, smart offices, and scientific research and education.

Figure: D1 Nezha Pin Diagram

The main features of the D1 Nezha are as follows:

• High-Frequency Performance: The D1 chip has a high frequency of up to 1.1GHz, which means it has extremely powerful processing performance. Among RISC-V chips, it's not common to see products that have been taped out and made into development boards, and they are mainly dominated by less powerful MCU-type chips. However, the emergence of the D1 chip has broken this situation. Its high-frequency performance not only makes Linux run more smoothly but also greatly enhances its playability.
• Supports RVV: The D1 chip supports RISC-V Vector Extension (RVV), which is a key feature in RISC-V for multimedia acceleration instructions. The version of RVV currently supported by the D1 chip is v0.7, while the latest officially released version is v0.10. With the V extension, the computing performance of the D1 chip has been significantly improved, especially in terms of image processing, audio and video processing, etc. This makes it an excellent choice for executing AI applications.
• Hardware Decoding Support: For audio and video processing applications, the hardware decoding function of the D1 chip has a significant advantage. This is a necessary function for executing Linux applications or multimedia application fields. By adding audio and video, camera, and other functions, the hardware decoding support of the D1 chip greatly enhances the playability and multi-functionality of the development board.

How to Choose the Right RISC-V CPU Development Board

Choosing the right RISC-V CPU development board is an important decision, as it will directly affect the performance and efficiency of your project. When choosing, you need to consider the following factors:

• Community Support and Documentation: An active developer community and detailed documentation can greatly enhance your development efficiency. The community can provide technical support to solve problems you encounter during development. Detailed documentation can also help you understand and use the development board faster.
• Hardware Interfaces and Peripheral Support: You need to ensure that the development board has enough hardware interfaces to support your project requirements. This may include interfaces such as GPIO, SPI, I2C, etc. In addition, you also need to consider whether the development board supports the peripherals you need, such as sensors, displays, network interfaces, etc.
• Core Architecture and Performance: RISC-V is an open-source instruction set architecture with many different implementations, including 32-bit and 64-bit versions. You need to choose the appropriate core architecture based on your application requirements. For example, if your application requires a large amount of computing power, you may need a more powerful core.
• Power Requirements and Consumption: For IoT devices, power requirements and consumption are very important considerations. You need to choose a development board that meets your power requirements and power consumption budget.
• Cost: Depending on your budget, you may need to consider the cost of the development board. However, remember that the cheapest option may not always be the best. You need to balance the cost with other factors such as performance, interfaces, scalability, and community support.

Since the hardware and software ecosystems of RISC-V are still in the development stage compared to ARM and x86, its maturity and stability may not be as good as the latter for the time being. Therefore, when choosing a RISC-V CPU development board, what we need to consider first is whether there is active community support and detailed documentation, as these can provide us with necessary technical assistance during the development process.

In addition, ensuring that the development board has sufficient hardware interfaces and peripheral support to adapt to project requirements is also crucial. Next, based on the specific requirements of the application, we need to choose the appropriate core architecture and performance. Especially for IoT devices, power requirements and power consumption are important factors that must be considered. Finally, when choosing a development board within the budget range, we need to make a balance among factors such as cost, performance, interfaces, scalability, and community support.

Conclusion

The RISC-V architecture, with its open-source, efficient, and flexible characteristics, has gained widespread attention and application worldwide. RISC-V CPU development boards, as physical implementations of the RISC-V architecture, offer developers and enterprises a cost-effective and versatile way to develop and test applications based on the RISC-V architecture. In this article, we have detailed four representative RISC-V CPU development boards, including HiFive Unmatched, VisionFive 2, BeagleV-Ahead, and D1-H Nezha, each with its unique advantages and application scenarios.

However, choosing the right RISC-V CPU development board is not an easy task. Developers need to make a comprehensive consideration based on their project requirements, budget, and factors such as the performance, power consumption, peripheral support, memory requirements, and community support of the development board. We hope that the introductions in this article can provide some useful reference information and suggestions for developers when choosing and using RISC-V CPU development boards.

The emergence of RISC-V CPU development boards marks the arrival of a new era in open-source hardware. As the RISC-V ecosystem continues to develop and improve, we believe that RISC-V CPU development boards will play their unique advantages in more fields, promoting global technological innovation and development.