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
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 Z400 Gaming Computer PC GeForce GTX 1060 256GB SSD 12GB RAM [Z400] - $825.00 : Professional Multi Monitor Workstations, Graphics Card Experts
How to install 16GB of memory/ram into an HP Z400 Workstation - YouTube
This is my HP Z400, upgraded with a Xeon X5690. 12gb of ram, 2x500gb SSD, 2x250gb HDD, GTX 960 (the gpu is totally overkill lol). This is my first server! Running pterodactyl