• The CPU is typically a computer's bottleneck, especially in pre-built systems.cpu 9 image by Robert Molnar from Fotolia.com
  
  

CPU Speed Controls All Calculations

• The speed of the processor (CPU) determines how many calculations per second a computer can perform, and this directly affects everything that the computer is used for. Increasing CPU speed will have a system-wide effect on all applications.
  
  

RAM May Be a Bottleneck

• If a system has a very low amount of RAM, it is possible that this is the speed "bottleneck," meaning that the only reason low speeds are noticed is because of the RAM. In this case, the CPU may not be working at its full potential and upgrading the RAM will remove this bottleneck.
  
  

Bottom Line

• If you have more than one or two gigabytes of RAM, then upgrading your CPU will make more of a difference than upgrading the RAM itself. Generally speaking, in modern computers the CPU tends to be a system's bottleneck until it has been upgraded at least once.