3 – Inside the computer: The CPU

Learning Outcomes

Objectives:

  • To understand that a CPU is made up of millions of tightly packed switches called transistors
  • To understand that transistors can generate heat which must be removed
  • To understand that the clock speed of a processor describes how many instructions can be processed each second

 

Must

watch the Royal Christmas Lectures on processors and be able to describe the concepts covered.  With help fill in the clock speed worksheet and be able to describe what clock speed is in simple terms. (Developing)

Should

watch the Royal Christmas Lectures on processors and be able to explain the concepts covered.  Fill in the clock speed worksheet and be able to explain the relationship between clock speed and how many instructions the CPU can carry out. (Meeting)

Could

watch the Royal Christmas Lectures on processors and be able to justify the concepts covered.  Fill in the clock speed worksheet and be able to justify the relationship between clock speed and how many instructions the CPU can carry out. (Exceeding)

Keywords

Words to learn for this lesson are:

Starter

When we looked at hardware, we mentioned the Central Processing Unit (CPU), often called processor for short.  All computers contain a processor, be it a mobile phone, tablet, laptop, desktop or server.

A CPU has legs on the bottom that connect it to the motherboard.  On top a heatsink and fan is fitted to remove heat from the processor.

Why do CPUs get hot?  Well they are made from millions of electronic components called “transistors” – these are essentially tiny electronic switches that can switch off or on.  If you could look at a CPU’s surface under a microscope you would see the transistors:

processor_microscope

In the picture above each transistor is spaced just 20 nanometres apart.  That’s really small, so how do processor manufacturers make them?

Main

Watch this part of the Royal Institution Christmas Lectures 2009 which explains just how fast processors can be (teachers – 6m40s to 10m23s – click here).

Watch this part of the video which shows how processors use switching to perform logic calculations (teachers – 12m1s to 13m29s – click here).

Watch this part of the video which explains why processors performing fast switching has resulted in fast processors (teachers – 27m12s to 28m28s (then do practical) – click here).

Watch this part of the video which goes through the problems of heat and why this is a barrier to processors getting even faster, along with the solutions that manufacturers have come up with (teachers – 31m13s to 35m04s – click here).

Plenary

Fill in this worksheet describing different processor speeds.

Homework