Different Types of Memory (AQA GCSE Computer Science): Revision Note
Exam code: 8525
Types of Memory
What are the different types of memory within a computer?
A computer system contains four main types of memory, they are:
RAM
ROM
Cache
Register
RAM and ROM are 'main memory', directly accessible by the CPU
Registers are covered in more detail here
What is cache?
Cache is very small, very fast memory located in the CPU which is used to provide quick access to frequently used instructions and data
The more cache there is, the more data can be stored, which speeds up the performance of the CPU
It prevents the CPU from having to repeatedly fetch frequently used instructions from RAM
Quick comparison
Memory | Role |
|---|---|
RAM | Stores programs and data currently in use |
ROM | Stores start-up instructions for the computer |
Cache | Stores copies of frequently used instructions to speed up execution |
Register | Super fast storage of instructions, data or addresses that the CPU is working on |
What is the difference between main memory & secondary storage?
Computer systems need both main memory and secondary storage to operate
Both play a crucial role in the operation of a computer system
A quick comparison of main memory and secondary storage shows:
Main memory | Secondary storage |
|---|---|
Volatile (with the exception of ROM) | Non-volatile |
Small capacity | Large capacity |
Why do you need main memory?
A computer needs main memory because access times are considerably faster than secondary storage
This means the time taken to complete operations such as the Fetch-Execute Cycle is dramatically reduced
Performance of main memory means a much higher cost which limits the amount that is used
For example, RAM is commonly purchased in 16 or 32 gigabytes whereas secondary storage such as a hard drive is in terabytes
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