^ you've asked a very good question that I've bear in mind for sometime now.
I really don't know why Orthos is only loading 1.20g~ mem for testing whereas on my DS3 Rev3.3 board it goes up to 1.92~95 like you said....

Are you using Vista as well?
Maybe something isn't configured right...I don't know who could help us...90% users/oc'ers are on XP...