Upgrading an hp z400 (six slots) - HP Support Community - 7156445
Malaysia HP Z400 / Z420 / Z600 / Z620 / Z800 / Z820 Workstation Memory 8G 1866 ECC
Acquired Z400 & xw8400 - which 1 to upgrade + issues - HP Support Community - 7346518
HP Z400 Workstation - Memory | HP® Customer Support
Upgrading an hp z400 (six slots) - HP Support Community - 7156445
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