I have BIOSTAR A55 ML2 Motherboard which supports DUAL CHANNEL RAM and also has 2 Ram slots, A1 and B1, Now the problem is that i purchased it with 4 GB DDR3 1333 Ram, Few weeks ago I retrieved a Spare Ram of 2 GB DDR3 1333 Ram, Now when plugged both ram to my motherboard, In PC Property It's Showing 6GB of total ram, But only 4 GB Usable, Even software CPUZ is showing single channel 6 GB Ram. It's Written on my Motherboard clearly DUAL CHANNEL DDR3 A1 B1, Please Help as I do not have such knowledge about RAM All I knew was that it should be same frequency to run 2 Ram together and motherboard should support dual channel which both are positive in my case then why am i not able to use both ram at same time and only 4 GB is usable even when it shows 6 GB in total.