hello sir please



you can't mix and match different types of memory. the cpu is designed to address one type of memory at a time. the memory type option is there to give users choice to use then-existing DDR2 ram without buying new and more expensive (at that time) DDR3 ram.

your listed motherboard has 3 revisions, i'm posting info from one only for reference:
http://www.gigabyte.com/products/product-page.aspx?pid=3505#sp
(Note: Mixed mode, populating DDR2 and DDR3 memory modules simulta- neously is not supported. Go to GIGABYTE's website for the latest supported memory speeds and memory modules.)
from the specifications page.