NEC Express5800 series User Manual page 207

9.
Lift the socket lever to allow the CPU to be installed.
IMPORTANT:
lever can be opened by 120 degrees or larger.
10.
Put the CPU on the socket carefully and slowly.
NOTE:
Note the direction of the CPU. To prevent the CPU from being
inserted into the mating socket incorrectly, a pin mark is put on both the
CPU and the socket. Check the pin marks to insert the CPU into the
socket correctly.
Open the lever until it cannot be moved any more. The
Pin mark
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