1. OCR GCSE Computer Science Teaching and Learning Resources
Chapter 2: Systems architecture
Cache memory
Cache memory is very fast memory located near to the CPU.
Data in cache can be accessed very quickly.

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Cache memory (cont.)
When data is required the CPU looks at the cache memory first.
If is not in cache it looks in main memory.
Data is copied from main memory into cache then to the CPU.
See the Chapter 2 animation: Cache memory.

3. OCR GCSE Computer Science Teaching and Learning Resources
Cache memory (cont.)
Cache memory is expensive so there is only a limited amount in a computer.
Cache close to the CPU will be the most expensive to produce but also the fastest.

4. OCR GCSE Computer Science Teaching and Learning Resources
Cache memory (cont.)
There are three levels of cache memory: Level 1, Level 2 and Level 3.
The level indicates the distance the cache memory is from the CPU.
L1 and L2 memory is located within the CPU.
L3 memory is on the computer’s motherboard.

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Cores
Many processors have multiple cores.
These cores can work together fetching, decoding and executing at the same time.
Multiple cores can process more data at the same time, making them faster.

6. OCR GCSE Computer Science Teaching and Learning Resources
Cores (cont.)

7. OCR GCSE Computer Science Teaching and Learning Resources
The CPU
The purpose of the CPU is to:
control the movement of data and instructions
fetch data and instructions from memory
decode and execute instructions

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The CPU (cont.)
The purpose of the CPU is to:
perform:
arithmetic operations, e.g. add and subtract
logical operations, e.g. AND, NOT, OR.

9. OCR GCSE Computer Science Teaching and Learning Resources
The CPU (cont.)
The performance of the CPU depends upon the:
processor speed
bus speed
amount of cache available
number of processor cores.

10. OCR GCSE Computer Science Teaching and Learning Resources
The CPU (cont.)
Some example processor specifications:
Processor L1 L2 L3
Cores
Speed
Core i7-4940MX
256KB
1024KB
8192KB 4
4000Mhz
Core i7-4960HQ
6144KB
3800MHz
Core i7-6567U
128KB
512KB
4096KB 2
3600MHz
Core i5-6440HQ
3500MHz
Core i5-6267U
3300MHz
Core i5-4288U
3072KB
3100MHz
Core i3-3220