Introduction to RISCV

Architecture

Computers will have a set of instruction set called ISA which will describe how the processor should be coded and excuted. More specifically, RISC-V comprises a small general base ISA and various ISA extensions compared to Complex Instruction Set Computing (CISC), which uses a large set of multiple instructions. CISC processors that use proprietary ISAs like Intel x86 and ARM typically require more cycle times to execute instructions (many times due to complex instruction getting multiple micro-coded instructions), while RISC-V processors can execute instructions in a single cycle. The smaller energy-efficient modular design of RISC-V with optional ISA extensions simplifies the instructions given to the processor to execute tasks. It allows developers to create a diverse array of custom processors for various markets quickly and efficiently.

Open-source ISA

An ISA (Instruction Set Architecture) defines the set of instructions a processor can excute. Open-source ISAs are freely available, allowing anyone to implement, modify, or extend them without licensing fees. RISC-V is the most well-known open-source ISA today, whereas ARM is proprietary but widely used.
RISC-V is an open ISAs, which means you are free to implement a RISC-V CPU in a microprocessor whithout having to pay royalties to anyone for using this ISA. The RISC-V ISA is considered the fifth generation of processors built on the concept of the reduced instruction set computer (RISC). It was designed as a modular ISA, as opposed to the traditional incremental ISAs. That means a RISC-V implementation is composed of a mandatory base ISA and a number of ISA extensions, so that custom CPUs may be tailored to the application’s needs.

RISC-V advantages

RISC-V has many advantages for developers and manufacturers compared to proprietary ISAs like x86 and ARM. The most notable include:

• Openness: RISC-V’s primary differentiator is its open-source nature. Unlike expensive propriety ISAs used in CISC processors, the RISC-V ISA is open to anyone and free of licensing and royalty fees. The RISC-V community-driven open ISA drives collaboration and innovation across industry. The open ISA instills transparency and trust with freely available ISA specifications and extensions that anyone can scrutinize.
• Versatility: Due to its modular design, RISC-V can cover diverse domains across various applications and functions, from data centers to embedded systems, machine learning modeling, high-performance computing environments, and IoT devices. RISC-V can handle more domain-specific requirements, adjust resources to accommodate changes in demand, and quickly scale, making it one of the most adaptable processors in the industry.
• Extensibility: Customizing the ISA to meet specific application needs is a crucial differentiator for the RISC-V architecture. RISC-V uniquely blends a modular design with the ability to add custom instructions to an open-source ISA. RISC-V can customize CPUs to their core, allowing developers to build application-specific processors that can improve performance and energy at the application level.
• Simplicity: RISC-V prioritizes simplicity by using a small set of ISA instructions with extensions that execute one instruction per clock cycle, unlike CISC processors that use a larger set of complex instructions that may require multiple clock cycles. With fewer and simpler instructions, RISC-V enables easier chip design making, reduces complexity, accelerates development cycles, and simplifies hardware and software optimization.

Applications

The applications of the RISC V processor include the following.

• RISC-V is used in embedded systems, artificial intelligence & machine learning.
• These processors are used in high-performance-based embedded system applications.
• This processor is appropriate to use in some particular fields like edge computing, AI & storage applications.
• RISC-V is important as it permits smaller device manufacturers to design hardware without paying.
• This processor simply allows the researchers and developers to design as well as research with a freely available ISA or instruction set architecture.
• The applications of RISC V range from small embedded microcontrollers to desktop PCs & supercomputers including vector processors.

In the next posts, we will do some hands-on projects with the RISC-V core on the Pico2 board to dive deeper into its real-world applications.