The Case for RISC-V

Here’s why we believe in RISC-V

The end of Moore’s Law Creates Opportunity

When the physicists and chemists were delivering 2x the transistors every 18 months, semiconductors were a big company game.  This created consolidation around two primary ISAs – ARM and x86.

However, Moore’s law is now broken – and its now taking 20 years to double transistor count.  This is happening at the same time as two key trends in semis that need dramatic improvements in price-performance curves – machine learning (ML) and the Internet of Things (IoT).

ML creates a nearly unlimited demand for processing resources and IoT grows the number of tiny edge devices into the 10s of billions – all of which need low cost and low power.

General purpose compute can’t address these problems as it has no more scaling path – thus the only way to address these needs is with architecture.  Specifically – there are three primary approaches that the industry must adopt:

1. More to more efficient programming languages -> C is 50x more efficient than Python.
   • The problem is software engineering efficiency and security.
   • A line of Python does 5-10x more than a line of C and programmers can write lines of code at a relatively fixed rate.
   • Lower level languages such as C require programmers to actively manage memory – this opens up a vast attack surface as mistakes in memory allocation expose systems to stack overflow, heap spray and many other forms of attack.
2. Specific workloads need to move off general purpose processors and on to hardware accelerators – be they GPUs, FPGAs or hardware blocks.
   • The price / performance improvement here is massive – 10-30x – however doing this on FPGAs or GPUs requires a large effort and it does not apply equally to all workload types.
3. Hardware architectures need to get refactored around application requirements.
   • This is where RISC-V comes in.

The end of Moore’s law means that processor architecture is in a state of disruption where small companies can innovate and add value again – from the gate level to the application level.

The Brilliance of RISC-V – Specialization without Fragmentation

What RISC-V allows is a common base set of instructions (ISA) that are universally supported and a toolchain that is able to handle both the base ISA and pass through customized instructions that a SoC architect can define.

This allows companies like Hex Five to develop a solution like MultiZone™ Security that will work everywhere, while still enabling SoC architects to customize the processor architecture – stages, cache sizes, hardware accelerators – or even create custom instructions to solve specific application issues without breaking compatibility and causing fragmentation.

In the ARM world you can do this with an architecture license (for ~$5M per core type), but when you make changes you also need to take ownership of the toolchain and supporting your developer community.  This has proven too much of a burden for even the largest companies to bear and they have given up on custom instructions.  This is ARM’s Achilles’ heel.

The Path for RISC-V Adoption

The Linley Group presented a vision of RISC-V adoption at the most recent Andes RISC-V CON on Nov 13, 2018.  It goes like this:

• RISC-V displaces custom in-house ISAs that OEMs have developed for peripheral functions (NVIDIA, HP, Qualcomm, etc.)
• AI Accelerators and small / low power applications adopt and apply RISC-V for their workloads to advance the price-performance curve.
• Vertical OEMs with their own SoC capabilities like Western Digital fully convert to RISC-V – look for more of these announcements at the RISC-V Summit in Dec
• Finally – mass market MCUs and MPUs begin to displace ARM in its core markets

The full presentation is available here : Linley Group – Andes RISC-V CON 11/13/18

This process will take more than 10 years; but the disruption it creates up and down the supply chain allows startups to innovate and grow in a way that is not possible on legacy architectures like ARM and x86.