1.2.1

CISC & RISC

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CISC & RISC Processors

Processors usually fall under one of two categories: CISC or RISC.

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CISC

  • CISC stands for Complex Instruction Set Computer.
  • CISC processors have a large instruction set built into it.
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CISC instruction set

  • The large instruction set allows programmers of assembly language to use fewer instructions as the instruction set built-in would deal with the additional needed steps.
  • Most of the built-in instructions are made up of multiple simple instructions.
  • Only about 20% of the built-in instructions were used in the average program.
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RISC

  • RISC stands for Reduced Instruction Set Computer.
  • A RISC processor has a small number of essential instructions built-in.
  • Each of these instructions can be completed in a single clock cycle.
  • This reduced instruction set means assembly programmers have to code more lines of code to achieve more complex results.
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CISC vs RISC

  • RISC processors have a library of simple efficient instructions whereas a CISC processor has a large library of complex instructions made up of simpler instructions.
  • A RISC processor has few addressing modes where a CISC processor has many addressing modes.
  • CISC processors are more expensive than RISC processors.

Jump to other topics

1Components of a Computer

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

5Legal, Moral, Cultural & Ethical Issues

6Elements of Computational Thinking

6.1Thinking Abstractly

6.2Thinking Procedurally

6.3Thinking Logically

7Problem Solving & Programming

8Algorithms

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