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Lesson 2 - Memory
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Lesson 2 - Memory
Revise, Recap, Review
Objectives
In your books, write down the three parts of a CPU and what they do
Write a definition and give an example of an embedded system
Lesson Objectives
Objectives
To be able to explain what RAM is and how it is used in a computer system
To understand the characteristics of and need for ROM
To understand how the use of virtual memory can improve system performance
Primary Memory
The CPU fetches data and instructions from memory to process.
The CPU CANT DIRECTLY ACCESS THE FILES from storage, only memory.
Accessing files from the hard drive would be too slow!
The two main types of primary memory are
RAM and ROM.
Primary Memory
RAM
RAM
Can be accessed at any time
Data copied from storage to RAM
RAM temporarily STORES THE PROGRAMS AND DATA YOU ARE USING
This includes the OS
Volatile
Data stored as electronic charge - needs to be topped up!
Question
If you are listening to some music while researching on the internet for information to use in a word processed document, what might be contained in RAM?
The OS
Music Player Software
Music Track
Web browser software
Web site being viewed
Word processor software
Word file
Anti-virus Software
DRAM vs SRAM
DRAM or SRAM?
Dynamic and Static
DRAM commonly found in RAM modules as it is cheap
Needs to be constantly refreshed to maintain data
SRAM much more complex (expensive) and retains data whilst power is present - without needing to be refreshed!
ROM
We already know that RAM can only work when the computer is turned on, and the cpu can't directly access files on the HD...........so how does the OS get into ram so that the cpu can access it?
ROM
The answer is using ROM!
In order to supply the instructions needed to start up the computer, the CPU needs access to permanently stored instructions - the boot program!
Non-Volatile
ROM needs to be non-volatile so that the boot program is remembered even when the power has been turned off!
ROM
The information in the ROM is placed on the chip by the manufacturer, and often contains the boot program - firmware
This Program:
Performs some basic system checks
Finds the OS and loads it into RAM
Hands over control to the OS
Why do you think we call this ROM?
Summary
Summary
Virtual memory
RAM is limited
When Full, we can move application data that hasn't been used for a while onto the hard disc
CPU can only read data from ram, so when it is to be used again it must be moved back to the RAM
Performance penalties - disk thrashing
Virtual Memory
Tasks
Answer the exam style questions on memory!
Shared:\Computing - ICT\KS4 - Computer Science GCSE (9-1)\Unit 1\Lesson 2\exam style questions
Using the exam vocab, answer the question using ALL of the key terms!
Task
Shared:\Computing - ICT\KS4 - Computer Science GCSE (9-1)\Unit 1\Lesson 2\construct an answer
Tell a friend!
Plenary
Explain to a peer what RAM is and how it is used
Have them explain to you what ROM is and why we need it
Discuss how virtual memory can be used to speed up a computer