i am having problems running my memory in dual channel mode , just installed a 7750 x2 black edition and am using the ram i already have . i have 4 gig of corsair xms2 ddr2 800mhz (4 x 1) , but with this new cpu it seems only to run in unganged mode (64 bit) . why is this ?

ps : my mobo is the gigabyte ma-770-ds3

i found this (below) on the gigabyte website in a faq for my mobo , but i cannot seem to find anything to change it

Q I have installed Phenom CPU and memory modules according to the Dual Channel Memory Configuration table in user’s manual, but system shows “unganged mode, 64-bit” during POST. How do I enable 128bit dual memory channel?
 

 
A Phenom CPU have two individual memory controllers (DCTs), each one of them controls single memory channel (64 bit). These two DCTs can work simultaneously when memory modules are installed on different memory channels. It is called “unganged mode”.

You can switch to “ganged mode, 128bit” when you are using two or four of the same memory modules. Please kindly enter BIOS setup program, to press CTRL+F1 key to enable advanced BIOS setup features then enter "MB Intelligent Tweaker(M.I.T.)\ DRAM Configuration", to set the “DCTs Mode” as “Ganged”.
 

yes but there is no option named "DCTs Mode" , but i have read that the unganged mode is 2x64 and it is faster than 1 x 128 . is this correct ?