Dell OptiPlex Gxi - Manual (Page 82)

If the replacement heat sink and microprocessor are separate, peel the thermal-pad protective cover off the bottom of the heat sink before attaching the heat sink to the
microprocessor.
To install the replacement microprocessor/heat sink assembly, ensure that the microprocessor-socket release lever is in its fully vertical position to allow the
microprocessor pins to easily slip into the socket. When the microprocessor/ heat sink assembly is in place, rotate the microprocessor-socket release lever to its
horizontal position. Hook the microprocessor securing clip over the socket tab nearest the right side of the system board, and then snap it over the tab on the opposite
side of the socket.
NOTE: Pin 1 on the microprocessor is located on the corner with the largest bevel. The pin-1 hole in the microprocessor socket is located on the
corner where the holes are in a diagonal pattern.