Which brand of SSD did you get? 300-read and 200-write seem kind of low for a sata3 SSD. Of the sata3 ports on your motherboard you may have two that are Marvell controlled and two that are Intel controlled , you can try the Intel controlled ports to see if that makes a difference. It does seem odd that you would have 3 sata3 ports since they are usually in even numbers , so you would either have two or four. If you could give brands and model numbers it would help.