ECS P4IBMS Instruction Manual page 22

Follow these instructions to install the CPU:
1. Pull the CPU socket-locking lever away from the
socket to unhook it and raise the locking lever to the
upright position.
2. Match the corner on the CPU marked with an arrow
with pin-1 on the CPU socket (the corner with the pin-
hole noticeably missing). Insert the processor into the
socket. Do not use force.
3. Swing the locking lever down and hook it under the
latch on the edge of the socket.
4. Apply thermal grease to the top of the CPU.
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