"eSata and USB3 PCIe card in Macpro 5,1
Installed the following eSata and USB 3.0 PCIe cards into a Macpro5,1 (mid-2012), both working fine under OS X 10.10.5, both purchased from eBay (AU) sellers for total cost of USD17 delivered.
AHCI Compliant 6.0Gbps Esata PCI-E PCI Express to SATA III 2 Ports Card using chipset: ASM106. (from eBay.com.au)
There are jumpers that need to be changed for enabling either the internal of external sata connectors (any 2 enabled at one time). Card shipped with internal sata enabled but I initially only tested esata. Wasn't until I tested an internal connector did I change the jumpers as I thought card didn't work.
Inateck® KT4004 4 port USB 3.0 PCI-e Card - chipset: FL1100. Apparently, listed as not compatible with Yosemite but tested fine so far with Seagate Expansion HD, Toshiba bus powered USB3, Sandisk usb2 card reader, various usb2 sticks.
USB3 speeds on Seagate 2TB Expansion Drive (NTFS formatted using NTFS for Mac OS X):
Other mods on Mac Pro: NVidia GTX660 2GB CUDA graphics, Samsung EVO840 SSD + Adapta-drive, Pioneer BDR-208D blu-ray burner, 32GB (4x 8GB) Hynix DDR3-1333 SDRAM Registered DIMMs.