Hp Z 400 mixed ram - HP Support Community - 7621103
16GB KIT (4 x 4GB) for HP-Compaq Z Workstation Series Z200 Z400 (4 DIMM Slots)
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
J9P81AA Certified Memory for HP Z400/Z440/Z600/Z640/Z800/Z840 4GB DDR4 ECC Reg. | eBay
HP Z400 Workstation MT Intel Xeon W3550 3.07GHz 8GB RAM No HDD No OS
HP Z400 almost 48GB ram Upgrade + RamDisk Benchmarks - YouTube
4GB RAM Memory Upgrade for HP Workstation Z400 PC3-10600E DDR3 1333MHz 2Rx8 ECC Unbuffered UB DIMM Module (MemoryMasters) at Amazon.com