• A CPU is the brain of a computer.cpu 1 image by Robert Molnar from Fotolia.com
  
  A Computer Processing Unit (CPU) is the brain of a computer and the greatest determining factor of speed and capability. A CPU manages the instructions given to a computer by the user and instructs other hardware how to react in an efficient manner. There are several qualities that determine a CPU's speed including the number of cores, the clock speed (measured in megahertz), transistor width (measured in nanometers) and cache memory (measured in megabytes). The world's foremost CPU manufacturers are Intel Corporation and Advanced Micro Devices Inc. Both offer an array of CPUs appropriate for low-end portable computers, mid-range desktop computers and high-end server machines.
  
  

Server CPUs

• Server CPUs are amongst the higher-end products on the market. They typically contain between four and six cores, have a clock speed of about 1300 megahertz, transistor width of 45 nanometers and a cache size of six to 12 megabytes. Server CPUs are optimized to run alongside other CPUs in the same machine to further boost processing power. Intel's server processor lines are the Xeon and Itanium CPUs. AMD's server lines are the Opteron CPUs. These products are used for businesses that are serving applications to hundreds or thousands of employees.
  
  

Desktop and Laptop CPUs

• Modern desktop CPUs typically consist of either two or four cores running at a clock speed of about 800 megahertz. The transistor width is 45 nanometers or 32 nanometers, and cache size is between 2 and 8 megabytes. Intel's line of CPUs appropriate for desktop computers include the Core i5 and Core i7 processors. AMD's desktop CPUs include the Phenom II and Athlon X2. Desktop and laptop CPUs are designed for consumer and business users who will perform computing functions such as multitasking, media viewing and editing; video gaming and Web-based activities.
  
  

Portable Computer and Netbook CPUs

• CPUs found in small computers such as portable Internet devices or netbooks are the lowest end products designed for simple computing tasks. These products typically contain one core, run at a clock speed of 533 megahertz, has an on-board cache memory of one megabyte or less; and a 45 nanometer transistor width. These CPUs are designed to conserve power and prolong battery life for portable devices. Intel's line of portable processors is Atom, and AMD's are the Sempron and Athlon Neo CPUs. These products allow for Web browsing, e-mail and Word processing capabilities.