Another way of getting a small speed boost is to ensure your RAM is configured in triple banks, that is 3 x 8 or 6 x 8 is faster than 4 x 8 or 8 x 8. An alternative is to use multiple AHCI SSD drives in a RAID0 (stripe) array to get even more performance. You cannot boot from newer NVMe type SSD drives but could potentially use one as a data drive. The fastest SSD you can use with a MacPro5,1 is an AHCI PCI based SSD and would reach nearly 1500MBps. First if you have RAM that supports 1333MHz your Mac will start using the RAM at that speed instead of your current 1066MHz, secondly the inter CPU connection speed will also increase to 6.4GHz. The general procedure for the 'Mid-2010' and 'Mid-2012' Mac Pro lines also is the same as it is for the 'Late 2009' models - slide the processor tray out of the computer, unscrew the heatsinks with a 3mm hex key, remove the heatsinks, clean off thermal paste residue, remove the processors, install the new processors, re-apply thermal paste. Having previously upgraded my own MacPro 2010 from 2 x 2.66GHz 4-core chips to 2 x 3.06GHz 6-core chips I can tell you that you will get a couple of additional bonuses. The definitive list of compatible CPU upgrades is here - Mac Pro CPU Compatibility List | MacRumors Forums The fastest CPUs you can upgrade to are 2 x 3.46GHz 6-core chips.

Best cpu for mac pro 5.1