Sli slowing down my pc`s gaming performance

[rarenoodle]

Hi guys .I seem to have the same problem as some people with 'sli'.I`m currently trying to sli n9600 gt 512`s.but when I enable sli in nvidia properties it seems to be worse than just with one card.I think its could be my PSU .Its just a 550w.thinking this is the problem.But the cards work fine with this amount of power available.please can someone give some thoughts? Thank you

 

[amuffin]

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