According to
http://i.dell.com/sites/doccontent/shared-content/data-sheets/en/Documents/dell-poweredge-r720-r720xd-technical-guide.pdf
all Memory for R720 is 1.35v. However other Information suggests that 1600 speed should be 1.5v.
Will low power 16GB 1600 speed (1,35v operable at 1.5v) modules work?