Sony PCV-RX460 - Manual (Page 64)

VAIO® System Reference Manual 50
Memory Module (DIMM) Slots
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 slot (a small triangle on the slot
indicates pin 1).
DIMM1 DIMM2
1 1 1 1
Indicates pin 1
Memory module (DIMM)