Transcript GCSEComputing_Session4

Session Objectives#4
COULD explain the function and purpose of the control unit, memory unit and ALU as
individual parts of a computer
SHOULD explain the role that primary memory plays in computer processing
MUST describe the differences between the main types of primary memory
Create solutions to the Little Man Computer assignment
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Computer Processing
STARTER: GO FOR 5....
Try to list 5 factors which affect how a computer performs.
Ext: For each explain what affect it has and why.
1.Size of processor
2.Amount of Cache Memory
3.Number of cores
4.Amount of RAM
5.Transfer speed of data buses.
BONUS:
Amount of free Hard Disk space...If a computer
is using all or it’s RAM it will use a section
of hard disk as a supplement. This is called
VIRTUAL MEMORY. However this is still slower
than pure RAM.
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Primary Storage
This is also known as Main Memory or Primary Storage.
INVESTIGATION (7 mins): Research what is known as the
‘bootstrap’ program of a computer. Take notes and prepare to
explain where and how is stored in the computer and why it is so
important.
This is the first instructions the CPU
receives when a computer is turned on
and is commonly called the BIOS (Basic
Input Output System). It contains code
which controls the basic hardware
settings of a PC. It is mainly stored
in ROM (Read Only Memory) which is NOT
erased when power is turned off.
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MEMEMORY – Remember??
To recap...
There are 2 main categories of memory:
RAM – Random Access Memory
This is volatile memory as it’s
erasable (without power) but can
be accessed quickly by the CPU.
ROM – Read Only Memory
This is non volatile as the data
Is retained without power. Therefore
Knows how to start up (or boot) after
Being turned off.
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4 Min Investigation
What type of memory is cache memory?
Are there any sub-divisions of memory? Create a
table and note their characteristics.
HomeWork – Investigate SRAM and DRAM. What are their
characteristics, differences and uses in terms of computer
processing.
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The Fetch-Execute Cycle
The CPU receives data and instructions in binary form. An
instruction will have 2 parts – an instruction and possibly some
data, a number or a memory location.
The programs that the CPU needs to process are stored in main
memory. The CPU simply fetches the next instruction it needs to
process, decodes it and executes it before repeating the
process.
Fetch
Excecute
Decode
The speed of this cycle is determined by an electronic Real Time
Clock (RTC) chip. The computer synchronises all processes to
this clock signal. The clock speed is measured in Hertz (Hz) or
cycles per second.
TASK: 500 Hz would be 500 cycles per second, how many could a
3GHz processor be capable of?
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Machine Code with
The Little Man Computer
Visit the following site and follow the simulations of the
Fetch-Execute cycle using the Little Man Computer (LMC)
http://www.cs.ru.nl/~erikpoll/III/dag4.html
This is an interpretation of how a processor handles machine
code.
TASK: Follow the instructions and make a note/diagram of where
the Little Man goes to throughout the Fetch Execute Cycle.
REMEMBER: Instructions are split into 2 parts, the instruction
(+,-, x, store etc) and the data itself (or memory
location/address of where the data to be used is stored)
1) The Op Code (or Operation Code Field) is part of the binary
code giving the instruction to be carried out i.e add or jump
2) The Operand (Operand Field or address field) gives the
address (memory location) where the data to be used in the
operation is stored.
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Little Man Code Library
CODE MEANING
1ab
Load
2ab
Store
3ab
Add
4ab
Subtract
500
Input
600
Output
700
Stop
800
Skip If Negative
801
Skip If Zero
802
If Skip Positive
9AB
Jump
Beware: the Little Man 0 is a positive number, so the instruction 802 is actually Skip if Non-negative.
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Little Man
Which parts of the processor does each LCM item belong to?
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System Block Diagram
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Little Man Machine Code Tasks
Assignments
1. Create a simple that will add any 2 numbers and display the
results.
2. Create a simple programs that will calculate the perimeter of
any rectangle.
3. Create a program using the LMC to allow the input of 2
integer values and then order them to output the largest value
first and then the smallest
RGB conversion SW
4. Colors of a pixel on a color are often represented with three
values (r, g, b) that the red, green and blue value
display. Grayscale on a monochrome display are represented by
only one gray value.
Choose a program that adds three inputs and divide by three, and
so rgb values to the grayscale.
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Flow Chart to LMC Assignment 1
START
Input A
Store A
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Input B
END
Store B
Output
Result
Load A
Add B
Coded Solution to Assignment
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00
01
02
03
04
05
06
500
299
500
298
199
398
600
INPUT A
STORE Value A at memory
location (address 99)
INPUT B
STORE Value B at address 98
LOAD A
ADD B
OUTPUT Result
Flow Chart
Flow chart of solution to LMC Assignment 3
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