will PCI E 2.0 4x support the full bandwidth of usb 3 or will it just bottle neck the usb

RE: PCIe Bus speed in Bytes/sec

--courtesy netkas.org

RE: USB3 Bus speeds

Although theoretically capable of 5 Gigabits/sec, or about 625 Mega Bytes/sec, USB-3 is also said to fall somewhat short of its theoretical maximum speeds.

No problem. Supports three full blast, four if there are any breaks at all.

It also depends... on what USB3 card, whether you have a 2009 4,1 or you have later model, the 4,1 'shares' the two 4x slots and depends what if anything the 4th slot is using.

There is a whole thread and rant on MacRumors "the state of USB3 and Mac Pro" as to what works or not and how well they work.

And just why. Because one disk drive isn't going to br eak the bandwidth bank, but there are other considerations, ejecting or not, do you plan to use some higher end RAID or Port Multiplier storage or such.

USB3 is going to be better than FW800 or USB2 of course. But it isn't bootable.

this card has been recommended by others

http://www.inateck.com/inateck-kt4004-4-port-usb-3-0-pci-e-express-card-without- power-connection/

I wonder: How does one buy that model? The Amazon links they provide lead to a visibly different model that requires power connections, and Amazon cannot find the model number KT4004.