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Computer Architecture and Processing Systems

Buses, input and output controllers and ports

  • 3 things to know
  • AS Unit 2

Overview

Bus in a computer system, three buses of a typical computer system and input/output controller.

What you need to know

Answer each one before you reveal it.

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Key term

What is a bus in a computer system?

Key term

Name the three buses of a typical computer system.

Key term

Why is the data bus bidirectional?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a bus in a computer system?

    Model answer

    A bus is a set of parallel lines that carries signals between the processor, main memory and the input and output controllers.

  2. 2

    Name the three buses of a typical computer system.

    Model answer

    A typical system has an address bus, a data bus and a control bus.

  3. 3

    What does the address bus carry, and in which direction does it travel?

    Model answer

    The address bus carries the address of the location or device being used, and it travels in one direction only, outwards from the processor.

  4. 4

    Why is the data bus bidirectional?

    Model answer

    Values must move both ways, into the processor when memory is read and out of it when memory is written, so the data bus carries traffic in either direction.

  5. 5

    Give three signals carried on the control bus.

    Model answer

    The control bus carries signals such as memory read, memory write and interrupt request.

  6. 6

    How does the width of the address bus limit a computer?

    Model answer

    The width of the address bus fixes how many separate locations can be reached, so a machine with a 16-bit address bus can address 65,536 locations and no more.

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