Sony PCV-L400 - Manual (Page 54)

VAIO Computer Reference Manual 46
Memory Module (DIMM) Connectors
Both sides of each Dual Inline Memory Module (DIMM) look very
similar. The side with pin 1 has a small "1" to the left of pin 1. Be sure to
orient a DIMM correctly in the DIMM connector (a small triangle on the
connector indicates pin 1).
OM04710A.VSD
DIMM2
DIMM1
1 11 1
Indicates pin 1
Memory module (DIMM)
OM04908B.VSD