CPU: AMD Phenom II X4 955 BE
current RAM: ADATA Premier 4GB DDR3 1333Mhz
MoBo: ASUS M5A88-M
I am going to buy a new RAM stick for dual channel & thinking of buying 4GB Corsair XMS 1600mhz DDR3.
If I add this memory to the same channel DIMM, will both memory sticks run in dual channel or I need a 1333mhz only?
(I know that both will run @1333mhz, but for good furture proof I want to buy a 1600mhz memory)
1600mhz will be good for overclocking.
Both memory sticks will be of 4GB (4+4=8GB).
You mean that you want to install the Corsair ram with the ADATA?
Yes you can do that, both will default to 1333 MHz, but it's highly recommend that you get 2 Sticks the same model and same specs because you might have instability with 2 different RAMs.
If the modules happen to work together, then you will get dual channel. However the problem you might run into is compatibility between the two - e.g., one module being one manufacturer @ 1333 and a different manufacturer @ 1600.
Ideally you want to match exactly to insure dual channel compatibility.
RAM is quite cheap these days, it wouldn't be too much more expensive to just buy a kit of 2x4GB at 1600. This way you can insure they'll work together. Plus, if you're thinking of OCing, doing the kit route opens the door to start doing that now.
FWIW, make sure you're using a 64bit OS; 32bit is maxed at 4GB.