Epson 4000 - Manual (Page 75)

5. Position the processor chip over the ZIF socket, aligning the
notched edge of the chip (marked with a dot) with pin 1 on
the socket, as shown below. A corresponding notch is
drawn on the circuit board under the socket.
Note
If you install the processor chip in the wrong orientation,
you may burn the chip and void your warranty.
6. Make sure the pins in the processor chip are directly over the
holes in the socket. Then gently push the microprocessor
straight into the socket, pressing evenly on all sides.
7. Close the ZIF by pressing the ZIF handle back to the closed
position.
4-28 Installing and Removing Options