How can I put heavy load on my CPU for a long period of time? How can I put my CPU under very high pressure for a long period of time? Are there programs for that that I can keep running ?
At the command line, run this command:

cat &lt; /dev/urandom &gt; /dev/null


(Open up a terminal window and type that into the window.)

This should keep your CPU loaded nicely for as long as you allow the command to run.