The card reader does basically what it should.
When reading my very fast Samsung 64GB SD card> 80MB / s read creates when in my external USB 3 card reader, it brings this card reader reproducible only on very 17 MB / s.
My 64GB CF card is, however, read in the same files with good 88 MB / s.
Why the USB 3 port with me does not function, I could not figure out.