CPU (Central Processing Unit)

The CPU, also called the processor or microprocessor, is the most important component in a PC. The CPU receives data input by the user, processes information and executes commands. In a PC, the CPU is housed in a single chip called a microprocessor.

Processor (CPU)

The main purpose of the CPU is to execute programs. It does this by doing three basic steps.

  1. The CPU uses it ALU (Arithmetic/Logic Unit) to perform mathematical operations like addition, subtraction, multiplication and division.
  2. Moving data from one location in memory to another.
  3. Making decisions and jumping to a new set of instructions based on those decisions.

The CPU uses the following to perform these functions:

  • Address Bus

    Sends an address to memory.
  • Data Bus

    Send or receive data from memory.
  • Read and Write Line

    Determines if it wants to set or get the addressed location.
  • Clock Line

    Uses clock pulse to sequence the CPU.
  • Reset Line

    Resets program counter and restarts execution.

CPU Speed and Performance

The performance of a CPU is measured in hertz by its clock rate. The "clock rate" is usually used to reference the speed of the CPU. The frequency of an oscillator crystal is used to determine the clock rate. However, clock rate alone can not be used to measure the performance of a CPU. An Intel CPU with a clock rate of 2GHz will be about twice as fast as the same CPU running at 1GHz with the same system components.

Other factors invloved in measuring CPU performance are:

  • Font side bus clock rate
  • speed and amount of installed memory
  • size of the CPUs bus
  • and amount of Level 1, 2 and 3 cache.

Clock rates can be misleading and should not be used to compare the performance of processors from different families or manufacturers.

64-bit Processors

Early processors ran in real mode and used a 16-bit data path. Current processors run in 32-bit protected mode. The next step is 64-bit processors. Both AMD and Intel currently have 64-bit processors released. Coupled with a 64-bit OS, a 64-bit CPU will drastically enhance the performance of demanding applications such as audio and video encoding, complex engineering programs like CAD and PC games.

A 64-bit CPU can handle more memory and larger files. Current 32-bit Intel and AMD chips can address up to 4GB of memory. In Windows-based machines, that 4GB is split between the operating system and the applications. That means the most memory any given application can access with the 32-bit version of Windows is 2GB. The 64-bit version of Windows can access up to 1TB (terabtye) of memory.

Multi-core Processors

A multi-core CPU contains two or more independent processors integrated into a single chip. Both AMD and Intel have multi-core CPUs available. A multi-core CPU is only beneficial if the software and Operating System being ran supports them.

CPU Cooling

A CPU generates a lot of heat and with PCs heat is your worst enemy. This is why all computer systems use some sort of cooling method to reduce CPU and case temperatures. Today's processors require cooling fans and a heat sink to keep them at a temperature level that will not damage the CPU. The heat sink is mounted on the CPU with a thermal compound placed between the heat sink and CPU. The thermal compound helps to draw heat from the CPU and transfer it into the heat sink, which usually has a fan mounted on it to better dissipate the heat. Higher end systems have as many as seven or eight fans mounted in the PC case to reduce temps. For extreme overclocking water or phase change cooling are often used.

Types of PC cooling methods:

  • Air Cooling (Fans & Heat Sinks)

    The most basic method of cooling. The function of air cooling is to simply draw in fresh air and expel hot air dissipated from the heat sinks using fans.
    Proper fan placement for air cooling
    Standard Air Cooling Setup
  • Water Cooling

    A method of cooling popular with overclockers. Water has a better heat absorbing property than air. The water absorbs heat from the CPU with a help of a CPU water block. Next the water is cooled down again as it passes through a radiator. Water cooling produces low temps and minimal noise for a very quite running PC, but is also expensive and invloves more risk and experience than air cooling.
  • Phase Change

    Phase change is the ultimate method of CPU cooling. Based on the same principles as an air conditioning unit or refrigerator, phase change happens when a liquid changes to a gas. A phase change cooling system requires four basic parts: A compressor, condenser, expansion valve, and an evaporator. There are a few potential problems with phase change cooling, including condensation and evaporator startup time.