Dell PowerEdge R940 Instruction page 7

Figure 6. Installing the PEM
10 Connect the 5UPI and clock cables to the PEM. Refer to the System Information Lable (SIL) for cabling.
11 Hold the PEM handle and rotate the PEM to closed position until it is firmly seated.
12 Remove the processor socket dust covers on the PEM.
13 Align the pins on the heat sink to the guides on the PEM and then place the processor and heat sink module (PHM) on the processor
socket.
Figure 7. Installing processor and heat sink module
14 Push the blue retention clips inward to allow the PHM to drop into place.
15 Using Torx #T30 screwdriver, tighten the screws on the PHM in the order below:
Upgrading the dual processor to quad processor system for the PowerEdge R940 7