title: How is CPU usage calculated?
body: <p>On my desktop, I have a little widget that tells me my current CPU usage. It also shows the usage for each of my two cores. </p>
  
  <p>I always wondered, how does the CPU calculate how much of its processing power is being used? Also, if the CPU is hung up doing some intense calculations, how can it (or whatever handles this activity) examine the usage, without getting hung up as well?</p>