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32GB (2x16GB) DDR3-1600MHz PC3-12800 ECC RDIMM 2Rx4 1.35V Registered Server Memory by NEMIX RAM at Amazon.com
CMS 32GB (2X16GB) DDR3 12800 1600MHz ECC Registered DIMM Memory Ram Upgrade Compatible with HP/Compaq® Workstation Z620 DDR3 for Server Only - B17 at Amazon.com