Apple recommends a DIMM installation scheme for the Mac Pro (Late 2013) that:

A.
Increases processing power

B.
Enhances graphics processing

C.
Optimizes system cooling

D.
Enables use of special memory modules

Explanation:
Apple recommends that you use Apple-approved DIMMs. You shouldn’t use DIMMs from older Mac Pro computers in your new Mac Pro. You can purchase Applebranded memory online from the Apple Store or by visiting an Apple Retail store or Apple Authorized Reseller .
https://support.apple.com/en-us/HT6054