NEC BladeServer Express5800 Series User Manual page 233

10.
Place the CPU in the socket carefully.
NOTE:
Note the direction of the CPU. To prevent the CPU from being
inserted into the socket incorrectly, a pin mark is placed on the CPU
and the socket. Check the pin marks to insert the CPU into the socket
correctly.
11.
Push the CPU lightly into the socket, and push down the CPU socket holder.
12.
Push down the lever to secure the CPU.
Upgrading Your Server 9-9