8GB Kit (2 X 4GB) DDR3 Memory Upgrade for Dell OptiPlex 780 Small Form Factor Desktop PC PC3-12800 240 pin 1600MHz RAM (PARTS-QUICK Brand) at Amazon.com
Solved: Upgrading my old Optiplex 780 - Dell Community
Solved: Optiplex 780, ram upgrade - Dell Community
OFFTEK 1GB Replacement Memory RAM Upgrade for Dell OptiPlex 780 (Desktop) (DDR3-8500 - Non-ECC) Desktop Memory at Amazon.com
DELL OPTIPLEX 780 USFF Intel core 2 Duo 4GB RAM 320GB HDD windows 10 pro WIFI | eBay