Amazon.com: HP Z400 Workstation PC - Intel Xeon W3520 2.67 GHz Quad-Core CPU, 24 GB DDR3 RAM, 2 TB Hard Drive, DVD-ROM, Windows 7 Professional : Electronics
Solved: Z400 RAM - HP Support Community - 6148900
4GB RAM Memory Upgrade for HP Workstation Z400 PC3-10600E DDR3 1333MHz 2Rx8 ECC Unbuffered UB DIMM Module (MemoryMasters) at Amazon.com
CMS 8GB (2X4GB) DDR3 10600 1333MHZ ECC Non Registered DIMM Memory Ram Upgrade Compatible with HP/Compaq® Workstation Z400 Workstation for Server Only - B80 at Amazon.com
Hp Z 400 mixed ram - HP Support Community - 7621103
HP Z400 Workstation/ SL605UC W3550 3.06GHz/ 6GB RAM/ 250GB HDD [Z400] - $349.00 : Professional Multi Monitor Workstations, Graphics Card Experts
A-Tech 24GB ECC Unbuffered Memory Kit (6 x 4GB) for HP Z400 Workstation - ECC UDIMM DDR3 PC3-10600 1333MHz 240-Pin DIMM 2Rx8 1.5V Dual Rank RAM (AM080899) at Amazon.com
How to install 16GB of memory/ram into an HP Z400 Workstation - YouTube