Dell XPS 17 (L701X, Late 2010) - Manual (Page 19)

Memory Module(s) 19
2 Align the notch in the memory module with the tab in the
memory-module connector.
3 Slide the memory module firmly into the memory-module connector at a
45-degree angle, and press the memory module down until it clicks into
place. If you do not hear the click, remove the memory module and
reinstall it.
NOTE: If the memory module is not installed properly, the computer may not
boot.
Memory-Module Connector
Number of Memory
Modules
DIMM A DIMM B DIMM C DIMM D
1
X
X
2
X X
X X
X X
3
X X X
X X X
4 X X X X
3
1
2