Primary Storage
- Primary storage is directly accessible by the CPU , it includes RAM, Cache, and ROM
- The purpose of Random Access Memory (RAM) is to store data, instructions and software (including parts of the OS) currently in use
- RAM is also called main memory
- RAM has faster read/write speeds than secondary storage
- RAM is volatile which means it is temporary memory and all data will be lost when the computer is switched off
- The larger the main memory, the more data the computer access quickly, which can improve the computer's performance
- A standard desktop computer has between 4GB and 16GB of RAM
- The parts of the operating system currently in use will be stored in RAM
- The purpose of cache is to store frequently/recently used instructions and data
- Cache has faster read/write speeds than RAM
- There are different levels of cache
- Level 1 cache is situated within the CPU
- Level 2 and 3 cache are situated on the motherboard
- If you increase the amount of cache you can store more frequently used data and increase the performance of your computer
- If you have too much cache it will decrease the data access speeds because the data requested will take longer to find
- Cache is volatile and all data will be lost when the computer is switched off
A diagram showing the parts of a computer system which are classed as primary storage
- The role of Read-only memory (ROM) is to store the computer’s boot-up sequence
- The boot-up sequence is a set of instructions the computer executes when then computer is initially switched on
- This sequence will run a series of checks to ensure all of the system hardware is working
- It will then load the operating system which will move from secondary storage to RAM
- ROM is non-volatile which means data will be stored when the computer is switched off
- ROM is read-only which means data cannot be written to ROM
The difference between ROM and RAM
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|
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Volatile |
Non-volatile |
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Can read and write data to RAM |
Read-only |
Exam Tip
- Make sure you're specific about which component you're referring to in exam questions and give the proper name e.g. RAM rather than memory unit
Worked example
Describe what is meant by main memory and how it is used in the Von Neumann model for a computer system
[3]
Any 3 of:
- Memory is RAM [1]
- It is primary storage [1]
- It is volatile memory [1]
- It holds currently in use data/instructions [1]
- It is directly accessed by the CPU [1]
