The CPU
Table of Contents
1 The CPU
The CPU lies at the heart of any Computer System, and is analogous to the brain in a human. There are many processors in a modern computer, but there is only one CPU.
Learn It
- A CPU is an integrated circuit that is responsible for performing arithmetic, logical and I/O operations.
- CPUs perform these operations as instructed by a computer program.
- A CPU is generally made up of two components
- An arithmetic logic unit (ALU)
- A control unit (CU)
Research It
- Find out the basic functions of the arithmetic logic unit and the control unit.
Document It
- Using no more than two sentences for each, describe the functions of the ALU and CU
Learn It
- A CPU works in 4 steps.
- Fetch - Instructions are fetched from the program in memory.
- Decode - Instructions are broken up for assignment to parts of the CPU
- Execute - Calculations and Logical operations are performed (such as addition)
- Writeback - Results of calculations are written back to memory.
Research It
- What is meant by a CPU's clock speed?
- What are the units of clock speed?
- What are the advantages and disadvantages of having a high clock speed?
Document It
- Make notes on the Fetch - Execute Cycle and CPU Clock Speed.
2 Multiple Cores
Processors have, in general, been getting faster and faster since their invention in the 1970s
Research It
- Find out what is meant by Moore's Law.
Learn It
- Even with exceedingly fast processors, they are still limited by the fetch - execute cycle.
- If you want to browse a web-page while listening to some music, a single processor would have to work on one task, and then switch to the next task, doing so thousands, millions or billions of times a second.
- By using multicore processors, the CPU acts as several independent processors.
- This means that one core can dedicate itself to your media player, while the other dedicates itself to the web-browser.
- Having multicore processors does not increase performance when working on a single task A 2.4GHz single core processor will be able to perform a single task (such as rendering a web-page) as quickly as a 2.4GHz quad core processor.
- Programmers are, however, beginning to utilise multicore processors in single applications, by dividing up tasks between cores.
Research It
- Find out about the specialisations of processors that are used in mobile devices.
Document It
- Ensure your notes contain information on Moore's Law, Multicore processors and mobile processors.
3 Graphics Processing Unit
In many modern computer systems, the task of rendering graphics is handled by the Graphics Card, which has it's own processor called a GPU.
Learn It
- GPUs are very specialised processors, designed to render graphics to a screen.
- A Graphics Card will contain, not only a GPU, but also its own dedicated RAM, that can hold a complete screen image.
- In many machines, the Graphics card is a separate device that is plugged into the Motherboard, but in laptops and mobile devices, it is often integrated with the Motherboard and so can't be upgraded.
Research It
Watch the video on what a GPU does.
Document It
- Ensure your notes contain basic information about Graphics Cards and what the roll of the GPU is in Computer systems.
Research It
- GPUs are now often used in Altcoin mining, such as Bitcoin
- Do some research to find out about how most crypto-currencies are mined, and why GPUs are more appropriate to this task than CPUs.