Computer architectureLesson 1 of 4 in the course Instruction set architectures

Instruction Sets: Compatibility, Encoding, Design, and Implementation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

An instruction set architecture (ISA) is the programmable interface through which software communicates with a processor. This lesson introduces the ISA as a contract that makes programs usable across compatible processor implementations.

An ISA is an abstract model of the behavior visible to software. It defines the machine instructions that programs can use, along with supported data types, registers, and rules for accessing memory. These rules may include addressing modes, virtual memory behavior, and memory consistency mechanisms. An ISA also describes the programmable input/output interface.

All flashcards

What is an ISA?
An instruction set architecture is an abstract, software-visible specification of a processor, defining instructions and other programmable features.
What is an ISA implementation?
A processor that carries out instructions specified by a particular ISA.
What is binary compatibility?
The ability of compatible processor implementations to run the same machine code, subject to relevant operating-system interfaces.
What is an ABI, and why does it matter?
An application binary interface defines conventions between compiled programs and an operating system; ISA compatibility alone does not guarantee compatibility across different ABIs.
What is the compatibility effect of an ISA extension?
An implementation supporting an extension can generally run older code that does not use it; code using added capabilities requires support for the extension.

Quiz questions

  1. What is the primary role of an instruction set architecture?Answer: It defines the programmable, software-visible interface and behavior of a processor.
  2. Which description best characterizes a RISC design approach?Answer: It emphasizes efficient implementation of instructions commonly used by programs.
  3. What responsibility do VLIW, LIW, and EPIC approaches place more heavily on compilers?Answer: Scheduling instructions to expose instruction-level parallelism.
  4. What is a common benefit of fixed-length instruction encoding?Answer: Instruction boundaries are generally simpler to locate and decode.
  5. How does microcode control instruction execution?Answer: It stores sequences of lower-level control steps for carrying out instructions.

Based on the Wikipedia article Instruction set architecture, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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