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
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
4GB RAM Memory for HP Workstation Z400 240pin PC3-8500 DDR3 UDIMM 1066MHz Black Diamond Memory Module Upgrade - Walmart.com
16GB KIT (4 x 4GB) for HP-Compaq Z Workstation Series Z200 Z400 (4 DIMM Slots)