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 Systemboard Intel 1333MHz LGA1366 586968-001 586766-002 [586968-001 586766-002] - $193.70 : Professional Multi Monitor Workstations, Graphics Card Experts
Upgrading an hp z400 (six slots) - HP Support Community - 7156445
4GB RAM Memory for Compaq HP Z Series Workstations Z400 Workstation (6 DIMM Slots) Black Diamond Memory Module DDR3 ECC UDIMM 240pin PC3-8500 1066MHz Upgrade - Newegg.com
HP Workstation Z400 Memory Upgrades @Memory.NET
HP Z400 Workstation
CMS 12GB (3X4GB) DDR3 10600 1333MHZ ECC Non Registered DIMM Memory Ram Upgrade Compatible with HP/Compaq® Workstation Z200, Z210, Z400, Z600, Z800 for Server Only - B81 at Amazon.com
Solved: Z400 X5690 W3690 Fastest Processors - HP Support Community - 5683601