Instruction Set Architecture(ISA)

# ISA

ISA는 하드웨어와 소프트웨어의 인터페이스라 할 수 있다.

 

명령어 집합(영어: instruction set) 또는 명령어 집합 구조(영어: Instruction set architecture, ISA)는 마이크로프로세서가 인식해서 기능을 이해하고 실행할 수 있는 기계어 명령어를 말한다. 마이크로프로세서마다 기계어 코드의 길이와 숫자 코드가 다르다. 명령어의 각 비트는 기능적으로 분할하여 의미를 부여하고 숫자화한다. 프로그램 개발자가 숫자로 프로그램하기가 불편하므로 기계어와 일대일로 문자화한 것이 어셈블리어이다.

 

An ISA is defined as the design of a computer from the Programmer’s Perspective.

This basically means that an ISA describes the design of a Computer in terms of the basic operations it must support. The ISA is not concerned with the implementation specific details of a computer. It is only concerned with the set or collection of basic operations the computer must support. For example the AMD Athlon and the Core 2 Duo processors have entirely different implementations but they support more or less the same set of basic operations as defined in the x86 Instruction Set.

 

# Microarchitecture

We note that the Microarchitectural level lies just below the ISA level and hence is concerned with the implementation of the basic operations to be supported by the Computer as defined by the ISA. Therefore we can say that the AMD Athlon and Core 2 Duo processors are based on the same ISA but have different microarchitectures with different performance and efficiencies.

 

# ISA vs. Microarchitecture

Now one may ask the need to distinguish between Microarchitecture and ISA ?

The answer to this lies in the need to standardize and maintain the compatibility of programs across different hardware implementations based on the same ISA. Making different machines compatible with the same set of basic instructions (The ISA) allows the same program to run smoothly on many different machines thereby making it easier for the programmers to document and maintain code for many different machines simulteneously and efficiently.

 

 

# Reference

https://ko.wikipedia.org/wiki/%EB%AA%85%EB%A0%B9%EC%96%B4_%EC%A7%91%ED%95%A9

명령어 집합 - 위키백과, 우리 모두의 백과사전

https://www.geeksforgeeks.org/microarchitecture-and-instruction-set-architecture/

Microarchitecture and Instruction Set Architecture - GeeksforGeeks