CPU

CPU

The purpose and function of a CPU (Processor) is to fetch, decode and execute instructions (process data) in a computer system
Components of the CPU
1. Cache
  1. Stores frequently/commonly used data
  2. Acts as a intermediary between the processor and RAM
  3. Larger Cache = Faster Processing; Saves fetching the instructions and data repeatedly from RAM – a relatively slow process which keeps the CPU waiting otherwise
2. ALU
  1. Arithmetic Logic Unit performs arithmetic calculations (e.g. Numbers) and logic functions (>,<,=,!=).
3. Control Unit
  1. Controls the flow of data transfers between CPU and the timing of operations in the computer.
  2. Checks that information have been delivered successfully between hardware/CPU
The “brains” of the computer; Computer cannot run without it
Stores Data into Main Memory once instructions are executed
Factors which affect the CPU's Performance
1. Cache Size
  1. Larger Cache = Faster Processing
  2. Has 3 levels
    1. L1 - Usually part of the CPU already and is the smallest and the fastest cache to be accessed
      1. L2 & L3 - Extra Caches that can be built between the CPU and the RAM. The more L2 and L3 memory available, the faster a computer can run. However, L2 and L3 cache takes slightly longer to access than L1 because it's further away from the CPU than L1
2. Clock Speed
  1. How fast the computer is at executing instructions per second
  2. Measured in Hertz
    1. 1GHz Processor executes 1 Billion Instructions per second
      1. 2GHz = 2 Billion 4GHz = 4 Billion etc.
    2. Number of Cycles per second
3. Cores
  1. The purpose of Cores is to allow more instructions to be done simultaneously
  2. Processors can have multi-cores
    1. Dual Core Quad Core 8 Core
    2. The amount of cores multiplies the number of instructions which can be executed
      1. e.g. 2GHz Single Core Processor executes 2 Billion Instructions 2GHz Quad Core Processor executes 8 Billion Instructions 2x4 = 8
Central Processing Unit
POST (Power-On-Self-Test)
1. A program used In the BIOS chip (Basic Input/Output System) which checks that all hardware and software is running properly
2. A message is sent to the monitor if the hardware/software isn't working properly
3. Happens when the computer system is 'booted up' (turned on)

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