x99 quad channel memory

Hey all i have a X99 gigabyte gaming 7 mobo. I have 2 sticks of 8 gigabyte (total 16gb) ram installed. Now i want to utilize the full quad channel bandwidth of my X99 mobo, do i have to install 8 ram sticks in total to occupie all the 8 slots on my mobo to have full bandwidth or do i have to...