Aaeon SBC-557 Manual page 26

3. Press the lever down. The plate will slide forward. You will feel
some resistance as the pressure starts to secure the CPU in the
socket. This normal and won't damage the CPU.
When the CPU is installed, the lever should snap into place at the
side of the socket.
Note:
When you install a new CPU, be sure to adjust the board settings,
such as CPU type and CPU clock. Improper settings may damage
the CPU.
16 SBC-557 User Manual
To remove a CPU, pull the lever out to the side a
little and raise it as far as it will go. Lift out the
CPU chip.