Give two reasons a long link is made serial rather than parallel.

Only one line has to be laid, which is far cheaper over distance, and there are no differences between wires to make bits arrive at different moments.

Crosstalk is interference induced in one wire by the changing signal in a wire running alongside it, which can corrupt the value being carried.

Why have internal parallel buses such as the old drive connectors been replaced by serial links like SATA and PCIe?

At very high signalling rates skew and crosstalk between the parallel lines put a ceiling on speed, whereas one well-shielded line can be clocked much faster and so carries more overall.

WJEC A-Level Computer Science 601-5345-3

Hardware: Architecture, Memory and Storage

Topic overview Components of a computer system and how they connect Von Neumann architecture and the CPU The fetch-execute cycle Memory and caching Parallel processing Input and output devices and their uses Secondary storage, fragmentation and defragmentation

Networks and Data Transmission

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Logic Gates and Boolean Algebra

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Database Systems

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Networks and Data Transmission

Serial and parallel transmission

3 things to know
AS Unit 1

Overview

Serial transmission, parallel transmission and bit rate and state its unit.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What is serial transmission?

Key term

What is parallel transmission?

Key term

Explain what skew is and why it limits parallel transmission.

Questions from this subtopic

Each one with the model answer underneath.

1
What is serial transmission?
Model answer
Serial transmission sends the bits of a message one after another along a single channel.
2
What is parallel transmission?
Model answer
Parallel transmission sends several bits at the same instant, each along its own separate wire.
3
Give two reasons a long link is made serial rather than parallel.
Model answer
Only one line has to be laid, which is far cheaper over distance, and there are no differences between wires to make bits arrive at different moments.
4
Explain what skew is and why it limits parallel transmission.
Model answer
Skew is the small difference in arrival moment between bits sent together, caused by tiny differences in the electrical properties of each wire; over a long line or at a high signalling rate the bits can drift far enough apart to be read as belonging to different groups.
5
What is crosstalk?
Model answer
Crosstalk is interference induced in one wire by the changing signal in a wire running alongside it, which can corrupt the value being carried.
6
Why have internal parallel buses such as the old drive connectors been replaced by serial links like SATA and PCIe?
Model answer
At very high signalling rates skew and crosstalk between the parallel lines put a ceiling on speed, whereas one well-shielded line can be clocked much faster and so carries more overall.

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Serial and parallel transmission

Overview

What you need to know

What is serial transmission?

What is parallel transmission?

Explain what skew is and why it limits parallel transmission.

Questions from this subtopic

What is serial transmission?

What is parallel transmission?

Give two reasons a long link is made serial rather than parallel.

Explain what skew is and why it limits parallel transmission.

What is crosstalk?

Why have internal parallel buses such as the old drive connectors been replaced by serial links like SATA and PCIe?

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Networks and Data Transmission, on a schedule.