5
5.2 Listening
transistors. If you look at the graph on Slide 2, you will see that while clock speed increased dramatically in the early days, the rate of growth has slowed. So, now we have two ways to increase speed, more transistors and higher clock speed. Finally, a third way to increase speed is to develop
multiple cores. Each core contains the Control Unit and the Arithmetic Logic Unit – the ALU and registers. The speed of the core is regulated by the clock. Basically, a core is a complete processor, which is linked to other processors as part of the same block of silicon. If you look at the graph, you can see that the first multicore chips began in 2005 and the number has increased considerably since then. OK. So, we have seen that there are three different ways to increase the processing power of a chip. Er … Where was I? Oh, yes … Now, I would also like you to think about the major
challenges in using the techniques I have just outlined. Actually, miniaturization is arguably the most important challenge for designers. The different circuits that make up a processor are created on a single block of silicon – which is the most common type of semiconductor – and it follows that the closer the components are to each other, the faster they can communicate. The gap or space between component parts is known as the process node and it is measured in very small parts of a metre – I mean, micrometres or nanometres (nm). This requires advanced design techniques and precision manufacturing and it’s essential there are very, very strict tolerances for the components. Both of these take a lot of time and are very
expensive. By the way, I should point out that making the gap smaller not only allows more components to be added, it can also reduce the power consumption of the processor as a whole. Naturally, reducing power usage is particularly appropriate for mobile devices, such as laptops, because these rely on limited battery supplies. However, even for fixed systems, such as desktops or servers which are not limited by battery power, the cost of power is a factor. The server farms needed for cloud computing run huge numbers of processors. So, reducing the rate of power consumption, which we measure in watts, while retaining or increasing the processing power is a significant challenge for designers. OK … now an interesting question which students often ask – which is more suitable for more powerful computing: faster clock speed or more cores? Well, this depends on what tasks you want the processor to complete … One way to think about it is to picture cars on a motorway – that’s a freeway if you’re from the US! If you have lots of slow cars, then a motorway with lots of lanes (or cores!) and a low speed limit (clock speed) will be best. However, if you have only two very fast cars, a motorway with a small number of lanes (so not many cores), but a high speed limit (clock speed) will be better.
F
Explain to students that being able to recognize these kinds of signpost phrase as they listen can help them to identify important points in a lecture. They’re very useful for identifying the overall structure of a spoken argument – for example, for seeing when the speaker is giving a definition, making an aside or drawing a conclusion.
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SKILLS BANK 5.1 Identifying signpost language in a lecture
You could ask students to say what they think each phrase is used for – either by inferring from the phrase itself or from memory. They could refer back to Skills Bank 5.1 at this point.
Set for individual work and pairwork checking. Give students time to read over the phrases.
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Play the recording. Elicit the answers, and feed back visually to the group.
Answers
3 – … by which I mean … 6 – Finally, … 1 – … firstly, … 7 – Basically, … 4 – Secondly, … 5 – … so, it follows that … 2 – … to return to the main point, …
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So, what are the ways in which computer processors have become more powerful? I’m going to focus on three key areas. Well, firstly, if we look at the graph in Slide 2, we can see that the number of transistors has increased hugely over time. By the way, I should point out there are other components of a processor: resistors, capacitors and diodes, for example. These components are a very important part of how the circuits work and we need to be aware that these are there, but for the purpose of measuring the processing power of the chip, it is the number of transistors that is important. So, to return to the main point, one way to make processors more powerful is increasing component density through miniaturization, by which I mean putting more components in the same space by making them smaller. Secondly, we can speed up processors by increasing
the clock speed. Remember that the clock speed shows how fast instructions are carried out by the processor, so, it follows that if the instructions are carried out faster, the chip will be more powerful. However, increasing clock speed is not as easy as increasing the number of transistors. If you look at the graph on Slide 2, you will see that while clock speed increased dramatically in the early days, the rate of growth has slowed. So, now we have two ways to increase speed, more transistors and higher clock speed. Finally, a third way to increase speed is to develop
multiple cores. Each core contains the Control Unit and the Arithmetic Logic Unit – the ALU and registers. The speed of the core is regulated by the clock. Basically, a
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