Introduction to RISC-V for Embedded Developers

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Benix Vincent Theogaraj - Watch Now - EOC 2022 - Duration: 26:06

Benix Vincent Theogaraj

Abstract Test Your Knowledge Questions & Comments (2)

The embedded software architecture has changed a lot in recent past.

Most of the embedded software has evolved from monolithic design to well abstracted, modular, scalable, configurable, and extensible in recent past.

However, the embedded processors on which these embedded software run did not undergo much change in this regard.

This talk discusses how RISC-V’s unique characteristics of its free and open ISA (Instruction Set Architecture) brings the modularity, extensibility, scalability, and customizability to embedded processor design.

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What is the primary practical benefit of RISC-V’s modular ISA (base ISAs plus optional extensions) for chip manufacturers, as described in the talk?

A They can pick and implement only the base ISA and extensions they need, avoiding packing unnecessary instructions and keeping designs clean and cost-effective.

B They must implement all standard extensions to claim RISC-V compliance, ensuring identical feature sets across vendors.

C It forces chip vendors to use a single monolithic ISA so software is guaranteed to be identical on every core.

D Modularity is only for documentation purposes and does not affect what instructions a silicon vendor may include.

E Modularity means every extension starts with Z and is automatically supported by all compilers.

If a vendor adds a custom RISC-V instruction (an X-extension) to accelerate a specific operation, what must they do for software to actually generate and use that custom instruction?

A Provide toolchain support (compiler/assembler) for the custom instruction so compiled code can emit it; otherwise standard toolchains will run but won't use the custom hardware.

B Nothing — standard RISC-V toolchains automatically detect and emit any vendor custom instructions at compile time.

C Register the custom instruction with the RISC-V Foundation before it can be used in any executable.

D Encode the custom instruction using one of the existing mandatory extensions (I, M, A, etc.) so compilers will accept it.

E Replace the base ISA with the custom ISA so that the core is no longer RISC-V compliant but the compiler will use the new opcode.

According to the talk, which combination of RISC-V design choices most directly enables easy scalability to many cores/harts on a platform?

A Each core keeps its own state in local CSRs and has its own instruction-fetch unit, while CLINT/PLIC define clear interrupt handling and harts may be time‑multiplexed — enabling independent, scalable cores.

B All cores share a single global instruction-fetch unit and a single set of CSRs so state is centralized for easier coordination.

C Harts must all progress simultaneously on their cores, which forces hardware to scale by adding identical synchronized pipelines.

D CSRs are memory-mapped in a single shared address space so software can directly manage any core’s state from any other core.

E Scaling requires removing privileged modes so all cores run in the same user mode and avoid interrupt arbitration.

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Upvotes Newest Oldest

Jay.Cosper

Score: 0 | 4 years ago | 1 reply

Thanks for the talk. Slide 6 shows a list of instructions, including NOP. But on slide 7 you discuss how no-operation was implemented. What it NOP then?

bvincentSpeaker

Score: 0 | 4 years ago | no reply

NOP is a pseudo instruction and it should be removed from slide 6. Thanks for pointing out !

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