Why are the USB 3.0 ports so slow on my brand new iMac? I am transfarring from an SD card using Delkin Devices card reader and first it takes about 30sec to about 1min for the card to appear on my desktop and then it gives me the time of like 8 hours to transfer 6GB than it reduces and ends up being way less BUT when I plug the same reader, the same card to my Mac Pro which is 3 years old and doesn't even support USB 3.0 the card shows up on the desktop immediately and I am able to open it and look at files and the transfer is super fast. What's wrong with my new machine?