Classification of ISA | Classes of Computer Architecture | CS School

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Classification of ISA or an Instruction set architecture (ISA) can be classified in number of different ways. In this Article we will discuss the types of computer architecture. Based on architectural complexity  number of Computer architecture as follows:

CISC, or Complex Instruction Set Architecture
RICS, or Reduced Instruction Set Architecture

A CISA has many specialized instructions which we rarely used in program. Such as it uses single instructions that execute several low level operation. As well as it is also capable of multi-step operations or addressing modes within a single instructions. Therefore RISC has been introduced to simplify processor by efficiently implementing only the instructions that we use frequently in program. So RISC allows processor to have fewer cycle per instruction (CPI) than a Complex instruction set Computer.

There are also closely related instruction set architectures that exploit Instruction level Parallelism with less hardware than RISC and CISC by making the compiler responsible for instruction issue and scheduling. So classification of those ISA as follows:

VLIW, or Very Long Instruction word,
LIW, or Long instruction word ,and
EPIC, or Explicitly parallel instruction Computing 

There is also ISA that are less complex to study, which are theoretically important types but have no commercial production. Such Instruction Set Architectures are:

Minimal Instruction Set Computer (MISC)
One Instruction Set Computer (OISC)

Read more article on Computer architecture here.

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