Characteristics Of The Cpu Ocr

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Exam code:J277

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

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 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)

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

A computer with more cores does not always run faster. Other factors can affect performance:

Software limitations: Some programs can only use one core
Task suitability: Some tasks cannot be split across multiple cores
Clock speed: A dual-core CPU with a higher clock speed might outperform a slower quad-core CPU
System components: Less RAM, smaller cache, or slower secondary storage can reduce performance
Virtual memory: Heavy use of virtual memory can slow down processing

1. State the purpose of the CPU	[1]
2. State what is meant by a dual-core 2.5Ghz processor	[2]
3. Von Neumann architecture contains registers. Identify two registers used in the Von Neumann architecture	[2]

Answer

1. State the purpose of the CPU	[1]
The CPU performs the FDE cycle Process instructions
2. State what is meant by a dual-core 2.5Ghz processor	[2]
Dual-core means there are two cores processing instructions 2.5GHs means it can run 2.5 billion FDE cycles per second
3. Von Neumann architecture contains registers. Identify two registers used in the Von Neumann architecture	[2]
Program Counter (PC) Memory Address Register (MAR) Memory Data Register (MDR) Accumulator (ACC)