A recent job posting by AMD suggests that RISC-V cores may appear in future designs, and their use could provide AMD with some significant advantages. What differentiates RISC-V from typical mainstream desktop processors, why would AMD consider integrating RISC-V into their future designs, and could RISC-V become a major contender in the desktop computing industry?

What differentiates RISC-V from typical mainstream desktop processors?

It has only been the past few years that RISC-V has received real media attention, with some calling it the architecture of the future. In contrast, others claim that it will replace ARM devices, while some even claim that RISC-V will replace mainstream processors such as Intel and AMD. But what exactly is RISC-V, and how does it differentiate itself from classical CPUs found in desktop PCs?

As the name suggests, RISC-V is a CPU architecture that uses a RISC model (Reduced Instruction Set Computing). As such, RISC-V focuses on CPU designs that are far simpler than those manufactured by Intel and AMD that use a CISC model (Complex Instruction Set Computing). This means that performing complex tasks on a RISC-V CPU may require more instructions (and therefore processing time) compared to running the same task on an Intel or AMD CPU.

However, simpler hardware allows CPU cores to use significantly less energy while simultaneously allowing for higher core density. Furthermore, the energy saved by RISC cores compared to CISC cores is not proportional, meaning that the energy consumed by CISC processors is generally an order of magnitude greater (if not more). This energy advantage is only enhanced with the ability to turn off individual cores combined with the use of parallel computing. Of course, CISC devices can turn off cores, but individual cores have far more complex circuitry that may not be in use.

Thus, a RISC-V CPU could be designed to have more cores than a standard desktop processor and consume significantly less energy but would take longer to complete complex operations.

But by far, the most important factor in RISC-V is that it is an open instruction set that requires no licensing or royalties (unlike every other core architecture, whether it is x86, x64, or ARM). This means that anyone able to design a processor can create a RISC-V compatible device with no strings attached.

Why would AMD consider using RISC-V cores?

AMD recently posted a job opening for experts in the RISC-V field who can design microarchitecture with both CPUs and GPUs in mind. This job opening strongly suggests that AMD is exploring the use of RISC-V in their future products, but why would a CPU designer consider using RISC-V?

Besides the fact that RISC-V is open source (and thus has no licensing or royalties attached), the energy savings offered by RISC-V could make it an ideal co-processor. The increasing regulations and requirements for electronic devices to minimise their energy usage is putting pressure on manufacturers to find ways to reduce their energy consumption, and CPUs are one of the biggest energy consumers in modern computers. Furthermore, the ability to reduce the energy consumption of a CPU also makes it ideal for use in portable applications such as laptops and tablets, as it will extend battery life.

The Apple M1 is an excellent example of a CPU that combines multiple CPU technologies to create a hyper-efficient device. While all cores on the M1 are ARM, some are designed for maximised computation while others are designed for low-power operation. This means that the core can assign tasks and disable cores depending on its current usage, and the use of ARM (which is a RISC CPU) has presented the M1 with significant energy savings compared to CISC CPUs. Thus, AMD could utilise the RISC-V architecture as a co-processor that allows the main CPU to power down and provide energy savings.

Could RISC-V become a major contender in the desktop computing field?

There is no doubt that the popularity of RISC-V will continue, and CPU architectures such as ARM are at serious risk of competition. However, it is doubtful that RISC-V will become the dominant CPU technology in desktop computing simply because desktop computing requires performance over anything else, and performance is generally maximised using CISC CPUs.

But this highly depends on the type of tasks that are being run. For example, a desktop PC running 50 different applications simultaneously may do better with a 50 core RISC CPU instead of a single CISC CPU, as each RISC core could handle each application independently. But a desktop PC running a resource-intensive task such as video rendering may fair better with a CISC over RISC (in this case, a dedicated GPU would do even better).

It is unlikely that RISC-V will replace any technology and will instead more likely become a key player in the co-processor world. If it replaces anything, it will be ARM, and even then, this is a difficult fight to win with the support that ARM has.