# GCSEComputing_Session3

```Session Objectives#3
COULD explain the role memory plays in computer processing
SHOULD describe the purpose of a CPU and its individual components
MUST identify components of a CPU
Explore key factors affecting computer performance.
GCSE Computing#BristolMet
Processing Components
Starter...
Convert the binary digits
denary)
10 1101
to decimal (also known as
32 16 8 4 2 1
X1 x0 x1 x1 x0 x1
=32 =0 =8 =4 =0 =1
= 32+0+8+4+2+1
= 45
All 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.
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Processing Components
The 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
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Processing Components
In 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.
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Processing Components
Main 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.
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Processing Components
Speed of data transfer...
TRANSFER SPEED INCREASES
Secondary
Storage
RAM
Cache
memory
CPU
TASK: Go shopping...Create a table and compare costs and
quantities of secondary storage, RAM and CPU with cache memory.
TYPE
Secondary Storage
RAM
CPU (with cache)
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COST
Quantity
Processing Components
Data 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.
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Block diagram of computer architecture
Main Memory (RAM)
Other devices,
Hard disk drives,
USB ports, DVD
drives
Front Side Bus (FSB)
CPU
(CU, ALU & LI
Cache)
Back Side Bus (BSB)
Southbridge
L2 Cache
L3 Cache
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Northbridge
RECAP
Learning 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?
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Processing Componets
A 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?
CPU Core & L1 Cache
CPU Core & L1 Cache
Back Side Bus
Interface to bus and
L2 Cache
TASK: Using sticky notes label as many internal parts of the
computer as you can.
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Processing Components
Consolidate 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 & ROM
5. Give a technical account of factors which affect computer
performance. (A*)
GCSE Computing#BristolMet
```

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