Here are my usb3 bench marks on a 6 year old mb . The type of drive you use wiil effect speeds I guess.
Is this an overclocked machine? I don't overclock my machine. I tested a 16GB Sandisk Cruzer Glide, the package said it was a USB3. Could it be I got a crappy USB3 drive, or is it that my USB3 is not set up properly on my machine?