Dell PowerEdge R810 Owner's Manual page 136

CAUTION:
The processor is held in its socket under strong pressure. Be aware
that the release lever can spring up suddenly if not firmly grasped.
9 Position your thumb firmly over the processor socket-release lever and
release the lever from the locked position by pushing down and pulling out
from under the tab. Rotate the lever 90 degrees upward until the processor
is released from the socket. See Figure 3-24.
10 Rotate the processor shield upward and out of the way. See Figure 3-24.
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Installing System Components