Characteristics of the CPU (Cambridge (CIE) O Level Computer Science)
Revision Note
Written by: James Woodhouse
Reviewed by: Lucy Kirkham
Characteristics of the CPU
What are the common characteristics of the CPU?
There are 3 common characteristics
Clock Speed
Cache Size
Number of Cores
Each of these characteristics has a significant impact on the performance of the CPU
How do the characteristics of the CPU affect performance?
Clock speed
The clock speed is measured in Hertz (Hz)
The clock speed measures the number of fetch-decode-execute cycles that can take place in 1 second
The faster the clock speed, the more instructions can be fetched and executed per second
Modern computers have a clock speed in Gigahertz (GHz), meaning billion
A clock speed of 3.5GHz can perform up to 3.5 billion instructions per second
Cache size
Cache is very small, very fast memory on or close to the CPU
Cache is used as temporary storage to provide quick access to a copy of frequently used instructions and data
The larger the cache size, the more frequently used instructions or data can be stored
This results in the CPU having to complete fewer fetch cycles from memory (RAM), speeding up the performance
Cache also has a significantly faster read/write speed than RAM, making it much quicker to retrieve instructions from there instead of from memory (RAM)
Number of cores
A core works like it is its own CPU
Multiple core processors mean they have multiple separate processing units that can fetch, decode and execute instructions at the same time
For example, a dual-core processor would have 2 processing units, each with their own
Control Unit (CU)
Arithmetic Logic Unit (ALU)
Accumulator (ACC)
Registers
Multi-core processors can run more powerful programs with greater ease
Multiple cores increase the performance of the CPU by working with the clock speed
Example: A quad-core CPU (4 cores), running at a clock speed of 3Ghz
4 cores x 3GHz
4 x 3 billion instructions
12 billion instructions per second
Worked Example
One computer has a single core processor and the other has a dual core processor.
Explain why having a dual core processor might improve the performance of the computer
[2]
Answer
Any 2 from:
The computer with the dual core processor has two cores/double the amount of cores [1]
Parallel processing can take place [1]
Each core can execute a separate instruction at the same time [1]
Each core can process instructions independently of each other [1]
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