RISC-V Design · All levels

Base Integer ISA (RV32I and RV64I) Execution Model - Interview Scenario

RISC-V ISA Fundamentals: scenario-based mechanism and closure drill.

Scenario

You are reviewing Base Integer ISA (RV32I and RV64I) Execution Model under RISC-V ISA Fundamentals.

diagram

OBSERVED METRIC
Instruction count mix, branch density, and CPI breakdown by ALU, load/store, branch, and control-transfer classes.

45-MINUTE INTERVIEW FLOW
0-5: define workload and KPI
5-15: map first mechanism failure
15-25: identify proving artifact
25-35: propose bounded fix with owner
35-45: define validation matrix and rollback

Expected depth

Mechanism to explain: The base integer ISA defines a clean load/store architecture: arithmetic and logical operations act only on registers, while memory is accessed through explicit load and store instructions. RV32I and RV64I share the same core design philosophy, with RV64I widening register and address operations and adding word-specific variants for 32-bit subword behavior. The ISA keeps the architectural state intentionally small and regular (32 integer registers plus program counter), making decode and hazard handling straightforward in simple pipelines while still scaling to out-of-order designs. Control flow is formed by conditional branches and jumps with well-defined PC-relative semantics, and the system model separates user-visible instructions from privileged behavior so implementations can reuse the base frontend across microcontrollers, Linux-capable cores, and accelerator-adjacent control processors.
Artifact to request: Base ISA execution map covering instruction classes, dataflow constraints, and implementation implications from single-cycle to superscalar pipelines.
Owners to include: CPU microarchitecture lead, compiler backend owner, verification lead, performance modeling owner, firmware and bring-up owner

Practice this lesson