Well hopefully that works, i can't see any reason why build 7100 wouldn't work either, from what i've read the previous builds (7077 for example) did support sli. But we are talking about Microsoft here, they aren't meant to make sense
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As for some games running worse with sli, there have also been some complaints (in these forums) about Crysotasis not supporting multi-cpu (or was it gpu?) and it appeared the game actually ran better on a weaker machine.
I guess it might be more common with games coming from the smaller teams of developers because they wouldn't have the ability to test on the various machines or to know what their engine is capable of running (and what won't run it..).
It is annoying to those who have recently beefed up their computer, but the upside is the games can be played by those who have computers that are a couple of years old too.