Sony PCV-RS100 - Manual (Page 64)

VAIO Computer System Reference Manual 48
Memory Module (DDR-DIMM) Slots
Align pin 1 of the Dual Inline Memory Module DDR-SDRAM DIMM to
the small triangle located on the memory module slot of the system
board.
DDR-DIMM1 DDR-DIMM2
Indicates pin 1
Memory module (DDR-DIMM)
1 1 1 1