I have Gskill ddr3 1600 runs at 1333 i want to go 4 more gigs of ram at ddr3 1333 will they still run in Dual Channel if the 1600 runs at 1333?
Yep those are mobo default settings.
You have to set-up your ram to vendors specs in the bios.
Plus i would suggest you add the exact same ram kit as the old one.
Silly having a 1600Mhz kit and adding another kit that's 1333Mhz.
If you put four 2GB sticks in, they will still run in dual channel. And if you have two 1600 sticks and drop in two 1333 sticks, you will be fine but more than likely you'll have to run them at 1333. You never know though, some RAM sticks are capable of more than their rating.
I have 2 x 2GB 1600 plus 2 x 4GB 1333 running in my i7 860, Gigabyte GA-P55M-UD2. I had the 2 x 2GB sticks for a year before adding the 2 x 4GB sticks, like you I opted for 1333's this time becaue of the difference in price. I tried OCing the 1333 by running them all at 1600 but it crashed. Haven't had time yet to play with settings and voltages to see what they are capable of so I just backed the settings down to 1333 and they run fine.