Hi
Please find below Memory Types Supported on this unit:
DDR3, RDIMM (Registered) or UDIMM (Unbuffered), ECC, LR (Load Reduction) DIMMs
For more information on this unit and for any upgrade, you may always refer to below document.
HP Z820 Workstation document
http://www8.hp.com/h20195/v2/GetPDF.aspx/c04111177.pdf
I hope that answers your question. 
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