The new top-of-the-line Mac Pro, 12-core “Westmere” 2.66Ghz and 2.93Ghz uses RAM new to Apple machines. These DDR3-1333 ECC DIMMs are 25% faster than the memory used in the previous generation Mac Pro.
Ramjet offers kits (http://www.ramjet.com/macpro.asp#3rdGen) containing 2GB, 4GB, or 8GB modules, up to the system maximum of 64GB. The 32GB kit (8x 4GB modules) is priced at US$3,550 from Apple and can be had for $1379.99 at Ramjet. For the true power-user, Ramjet offers a mammoth 64GB kit, not even available from Apple, for $2,839.99.
Ramjet memory includes a lifetime warranty, and you can send your original RAM back to Ramjet for a rebate.