Dell XPS 8500 (Early 2012) - Manual (Page 106)

Postrequisites
1 Replace the processor fan and heat-sink assembly. See "Replacing the
Processor Fan and Heat-Sink Assembly" on page 99.
2 Replace the computer cover. See "Replacing the Computer Cover" on
page 25.
3 Follow the steps in "After Working Inside Your Computer" on page 15.
Processor 106