8GB RAM Memory for Compaq HP Z Series Workstations Z420 Workstation Black Diamond Memory Module DDR3 ECC Registered RDIMM 240pin PC3-8500 1066MHz Upgrade - Walmart.com
A-Tech 32GB ECC Registered Memory Kit for HP Z420 Workstation (4 x 8GB) ECC RDIMM DDR3 PC3-12800 1600MHz 240-Pin DIMM 2Rx4 1.5V Dual Rank RAM Upgrade | Pricepulse
Memory Ram 4 HP Workstation Z1 Z420 Z620 Z820 Only Upgrade 1,2x Lot DDR3 ECC UK | eBay
RAM upgrade does not work - HP Support Community - 7963250
Z420 updgrade options - HP Support Community - 7648864