A guide to accelerating applications with just-right RISC-V custom instructions | Lee Moore, Duncan Graham, Embedded Magazine

The open instruction set architecture (ISA) of RISC-V permits broad flexibility in implementation and offers optional features that can enable fresh approaches to resolving hardware-software design tradeoffs. Based on a modular structure, a number of standard extensions and options can be used to configure the base processor as a starting point. Yet the true value actually lies in the opportunities that RISC-V offers developers to create new extensions, instructions and configurations that uniquely meet the needs of their innovative application ideas.
Article: https://www.embedded.com/a-guide-to-accelerating-applications-with-just-right-risc-v-custom-instructions/