How to Design an ISA.

This article discusses the intricacies of designing instruction set architectures (ISAs), emphasizing their crucial role as a lingua franca between compilers and microarchitecture. It highlights the importance of optimizing ISAs for different source languages and microarchitectures, addressing trade-offs between encoding efficiency, instruction density, and microarchitectural complexity. The author argues against oversimplified beliefs that ISAs don't matter much compared to microarchitecture, stressing that a well-designed ISA can significantly impact performance and power consumption, particularly in complex cores. Additionally, the article explores how certain ISAs, like RISC-V, make design choices that impact emulation and compatibility with legacy software, underscoring the challenges and trade-offs inherent in ISA design.