Better performance when SLI is disabled???

So I've had this rig for a few years now.
i5 650 stock speed 3.2ghz
gigabyte p55m-ud4
Kingston 4GB 1333
SLI 9800GT
450 Ultra PSU

Today when I started up Kerbal Space Program in full screen (1920x1080) everything was in shades of green and red. So i took the cards out and put them back in. Then there wasn't even any DVI signal. So eventually I tried running with only one card. It was GPU 2 when I was running SLI. Now i notice less lag in games than I got when I was running them in SLI. How can this be that I get better performance with only one card? I'm getting a new gpu soon but i'm just wondering why this is happening
4 answers Last reply Best Answer
More about performance sli disabled
  1. It could be that what you think is lag is actually micro-stutter.
  2. No it was definitely lag. With sli i got 15 fps in kerbal space program and now I have 25
  3. Best answer
    Your psu isn't capable of supplying enough power. 450w is only enough for 1. This issue is only seen in low quality psus and will kill your components if you continue to do this. Voltage regulation has to work harder when not supplied with enough power. Better quality psus will have safety measures against this. I suggest not using ultra psus at all, they are just detrimental.
  4. Okay well i'm getting a 7970 or 7950 with an EVGA 750W psu so I think i'll be good
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