Intel recently announced that it would be using RISC-V in its next generation of Nios V soft IP microcontrollers for FPGAs. Why is RISC-V being introduced by multiple vendors, what features will the Nios V soft processor offer, and could RISC-V see the fall of ARM?

Why is RISC-V being introduced by multiple vendors?

RISC-V (pronounced “Risk Five”) is an upcoming processor architecture that has many similarities to ARM in that they are both reduced instruction sets, are designed with energy efficiency in mind, and are both ideal for technologies such as mobile computing and microcontrollers. While ARM has the significant advantage of being well supported with decades of development, RISC-V has the advantage that it is open-source and therefore has no licensing or royalty fees.

It is most likely that the lack of fees and transparency surrounding RISC-V is why many vendors are looking towards its use as a replacement for ARM. Furthermore, the potential takeover of ARM by Nvidia could dissuade ARM users from fear that Nvidia may interfere with ARMs policy of neutrality. While software support for RISC-V is nowhere close to what ARM has, its introduction from different vendors will soon see this change.

Another reason for getting into the RISC-V game early is that it can potentially see a company recognised as an early adopter. This is generally important for those who want to be seen as innovators and developers. This can see early adopters help direct the development of RISC-V in a favourable direction.

Intel to use RISC-V in their NiosV soft processor

Recently, Intel announced that it would be using the RISC-V RV32IA architecture in its next generation of Nios V processors. These processes are soft IP, meaning that they are not a physical product but intellectual property that FPGA users can program into their designs. One significant advantage of using IP processors in an FPGA is that it allows for updates and improvements over time which can boost performance in the future.

The Intel Nios V processor is aimed explicitly for microcontroller applications that utilise Intel FPGAs, including the Intel Cyclone, Intel Arria, Intel Stratix, and Intel Agilex. The processor’s performance is 0.464 DMIPS/MHz when using a 4KB on-chip instruction bus, 4KB on-chip data bus, Avalon Memory-Mapped pipeline bridge, and Intel Quartus Prime software.

Compared to the ARM M0+ core, the Nios V has approximately half the performance. Still, the primary focus of the IP is for use in specific applications that utilise hardware and other circuitry for specialised functions. Furthermore, the use of RISC-V allows for additional instruction extensions to be added that can help boost the performance of the core. Intel is also working towards a general application class processor for running operating systems such as Linux.

Could RISC-V replace ARM in the long term?

RISC-V eliminating ARM from the picture would be difficult due to the widespread use of ARM and the overwhelming software support offered by ARM. It should also be noted that ARM being closed-source and proprietary means that ARM will also provide unique services to customers, including support, debugging, customisation, and consolation, whereas RISC-V offers none of this.

ARM also offers IPs to pre-designed customers and require the end-user to have little to no knowledge of ARM core design. RISC-V, however, is only an instruction set architecture that requires users to understand how to design a CPU from the ground up.

However, CPU specialists will most likely start to produce RISC-V processors for other manufacturers to use in their designs (such as Intel is already doing). The removal of licensing fees and royalties and CPUs that all use the same instruction set would see designs that could accept software from multiple vendors with little need for changes (depending on the hardware configuration).

For example, most desktop computers use the Intel x86 architecture, but only a handful of companies can produce such processors. If RISC-V became the norm in the computing field, then computers would have a far wider range of potential processors to choose from. However, RISC-V is not designed for high-performance computing, and therefore will be unlikely to replace x86.

Unless ARM can meet the rising challenge of RISC-V with different pricing options, better architecture, or easier access, then RISC-V could become a significant processor architecture in the next decade.