Mac Pro memory compatiblity

Solution
Mac Pro (Mid 2010) variants support 4 x 4 GB or 8 x 4 GB based on the Processor ( Official Spec).
Unofficially it is speculated to work with up to 32GB (4 x 8 GB) and 128 GB (8 x 16 GB) respectively.

Supports DDR3 Unbuffered ECC Memory 1066 MHz and 1333 MHz. Operates at 1.5v. 16 GB sticks may operate at 1.35v.

Note: Based on the processors, the speed at which your MacPro can work will differ. 1600 MHz is not recommended by Apple and may not work for sure.
Mac Pro (Mid 2010) variants support 4 x 4 GB or 8 x 4 GB based on the Processor ( Official Spec).
Unofficially it is speculated to work with up to 32GB (4 x 8 GB) and 128 GB (8 x 16 GB) respectively.

Supports DDR3 Unbuffered ECC Memory 1066 MHz and 1333 MHz. Operates at 1.5v. 16 GB sticks may operate at 1.35v.

Note: Based on the processors, the speed at which your MacPro can work will differ. 1600 MHz is not recommended by Apple and may not work for sure.
 
Solution