Lenovo IdeaCentre B520 - Manual (Page 46)

Hardware Maintenance Manual
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8. Lift the microprocessor straight up and out of the socket.
Note
a. Note the orientation of the notches 1 on the microprocessor.
This is important when installing the new microprocessor on the
motherboard.
b. Do not drop anything onto the microprocessor socket while it is
exposed. The socket pins must be kept as clean as possible.