OFFTEK 1GB Replacement Memory RAM Upgrade for HP-Compaq Workstation Z400 (6 DIMM Slots) (DDR3-10600 - ECC) Server Memory/Workstation Memory at Amazon.com
How to install 16GB of memory/ram into an HP Z400 Workstation - YouTube
Rare find: HP Z400 Workstation - Iconic vintage High End computer - Intel Quadcore Xeon - 16GB RAM - 1TB Hard - Computer - Heavily upgraded! - Catawiki
A-Tech 4GB for HP HP Z400 Workstation (6 DIMM Slots) (1 x 4GB) PC3-12800 (DDR3-1600) ECC Unbuffered UDIMM 240-Pin 1Rx8 1.35V Server Memory RAM at Amazon.com
4GB RAM Memory Upgrade for HP Workstation Z400 PC3-10600E DDR3 1333MHz 2Rx8 ECC Unbuffered UB DIMM Module (MemoryMasters) at Amazon.com