Dell XPS 15 (L521X, Mid 2012) - Manual (Page 56)

6 Remove the screws that secure the system-board assembly to the
palm-rest assembly.
7 Lift the system-board assembly at an angle and release the ports on the
system board from the slots on the palm-rest assembly.
8 Slide and remove the system-board assembly from the tab on the
palm-rest assembly.
2
1
3
1 screws (5) 2 system-board assembly
3 tab
9 Turn the system-board assembly over.
10 Remove the primary memory-module by following the instructions from
step 1 to step 2 in "Removing the Memory Module(s)" on page 23.
56 | Removing the System Board