Serial, parallel, simplex and duplex
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 4 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Two questions
- Serial and parallel
- Skew
- Serial against parallel
Read the transcript of the teaching part
Last time
Before we start: last time, in Compression, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Two questions
Every time data travels down a cable, Cambridge asks two questions. How many bits go at once: serial or parallel? And in which direction: simplex, half-duplex or full-duplex?
Serial and parallel
Serial sends data one bit at a time, down a single wire. Parallel sends several bits at the same time, down several wires.
Skew
Parallel sounds faster, so why not use it everywhere? Because over a long cable, the bits on different wires arrive at slightly different times. That is called skew. The receiver gets the bits out of step, and the data is wrong. So parallel only works over very short distances.
Serial against parallel
Serial: bits arrive in order with no skew, it is reliable over long distances, and one wire is cheaper. But it is slower. Parallel: faster over short distances, but it suffers skew, needs more wires, and costs more.
Chapter 2.2: Data transmission
- Serial, parallel, simplex and duplex 5 min
Also for IGCSE Computer Science 0478
Which topics come up most in IGCSE Computer Science 0478 past papers, counted from every paper since 2004: Paper 1 topic frequency, Paper 2 topic frequency.