Had a Gigabyte Z77 D3H v1.1 (F22 bios) for a number of years and...
Just bought a SanDisk Ultra Flair 32 GB USB 3.0 stick. Been testing it with crystaldiskmark and usb flash benchmark, with both giving similar results. That is, when I first plug the stick in, I get results about one third of those expected. If I then physically remove (software eject first) and insert it in the same socket, then re-run the benchmark, I get about the expected/rated speed. I don't know if its normal behaviour or if there's a problem, but obviously I don't want it defaulting at the lower speed if I need to use it for a bootable/install Win10 O.S (its main purpose).
(Running the benchmark twice without removing the stick gives the same slower result)
First time plugged in
Second time
Thinking it might be a motherboard bios setting or driver related.