Sony PCV-RX780G - Manual (Page 62)

VAIO Digital Studio System Reference Manual 48
Memory Module (DDR-DIMM) Slots
Align pin 1 of the Dual Inline Memory Module (DDR-DIMM) to the
small triangle located on the memory module slot of the system board.
DDR-DIMM1 DDR-DIMM2 DDR-DIMM3
Indicates pin 1
Memory module (DDR-DIMM)
1 1 1 1