Session Objectives #3

GCSE Computing#BristolMet

Session Objectives#3

MUST identify components of a CPU

SHOULD describe the purpose of a CPU and its individual components

COULD explain the role memory plays in computer processing

Explore key factors affecting computer performance.


Processing ComponentsStarter...Convert the binary digits 10 1101 to decimal (also known as denary)

32 16 8 4 2 1X1 x0 x1 x1 x0 x1=32 =0 =8 =4 =0 =1= 32+0+8+4+2+1

= 45All instructions and data are stored in a computer as binary numbers. The organisation and structure of a computers’ processing components is known as computer architecture.


Processing ComponentsThe Central Processing Unit (CPU or Processor)This is the core of every computer system and it processes instructions from the various programs that are running.They consist of 2 main components:i)the Control Unit (CU) which uses electrical signals to direct the system to excecute the instructions in stored programs. It controls the order and flow data to be executed

ii)The Arithmetic and Logic Unit (ALU) which carries out all the mathematical and logical operations i.e addition, subtraction and comparisons (relational operations such as =, < and >)

Think of the CU as a traffic controller

and the ALU as a professor


Processing ComponentsIn order for a processor to function it also needs to access Main Memory or RAM (Random Access Memory) where the program data is stored whilst in operation (which have been fetched from the hard disk)

Cache memory is used to store data whilst waiting to be processed, which enables the CPU to fetch the data it needs much quicker then going back to the main memory. You can consider this as a special type of RAM.

ROM (Read Only Memory) – It useful to introduce this at this stage. This data can not be overwritten and the CPU will look to a store of this for the first program to load and exexute when turned on, known as the boot sequence. This data is NOT lost when the power is turned off.


Processing ComponentsMain Memory (RAM) & Cache Memory are called Primary Storage (or Primary Memory).

Knowledge Gap - What is secondary storage...?

Cache memory is very fast memory and is located close to the CPU. It also a lot more expensive compared to standard RAM. Modern computers have Level 1 (L1), L2 and L3 Cache memory with the numbers referring to the distance from the CPU in that order. L1 is built into the chip itself. L3 is further away on the motherboard (Printed Circuit Board PCB) .

The closer the cache the faster the CPU can access the data and execute instructions.

NB Cache Memory and RAM are both known as volatile memory since they can be erased, which allows them to take on board new data. They also need power to store data.


Processing ComponentsSpeed of data transfer...

TASK: Go shopping...Create a table and compare costs and quantities of secondary storage, RAM and CPU with cache memory.

What are your conclusions?...

TRANSFER SPEED INCREASES

Secondary Storage CPURAM Cache

memory

TYPE COST QuantitySecondary Storage

RAMCPU (with cache)


Processing ComponentsData BUSES – the processing components are connected on the motherboard via circuits called buses which allow the transfer of data and control signals. The speed of the buses also affect how fast a computer can perform operations.

TASK: Attempt to draw a block diagram illustrating the architecture of the given example.


Block diagram of computer architecture

CPU(CU, ALU & LI

Cache)

Northbridge

Southbridge

L2 Cache

L3 Cache

Main Memory (RAM)

Front Side Bus (FSB)

Back Side Bus (BSB)

Other devices,Hard disk drives, USB ports, DVD

drives


RECAPLearning check – what do we now know???

Name the 2 components of a CPU?

What are they used for?

What is primary storage and what does it consist of?

How is data transferred around a motherboard?


Processing ComponetsA dual-core processor simply has 2 CPU’s working together. They may both have their own cache memory or may share L2 or L3 cache but since they can fetch, decode and execute instructions at the same time so the computer is able to process more instructions as a whole. What affect will this have on performance?

TASK: Using sticky notes label as many internal parts of the computer as you can.

CPU Core & L1 Cache CPU Core & L1 Cache

Interface to bus and L2 Cache

Back Side Bus


Processing ComponentsConsolidate learning:

Questions:

1. What is the purpose of the CPU in a computer?2. What is a dual-core processor? What are the names given for CPUs with 4

cores, 6 cores and 8 cores??3. Describe how cache memory and RAM are used by the CPU?4. Explain the differences between RAM & ROM5. Give a technical account of factors which affect computer performance.

(A*)

Documents

Session Objectives #3