Ok, my motherboard says it has 2 pci 16x slots, but they operate at 8x speed. Does this mean that with my one 7900 GS card it is only using half of the bandwidth? This would explain a lot because my card is getting about half of the FPS on 3dMark06 compared to other systems. I guess I would like an answer to my question plus a description of pci 8x(sli) and the pros and cons? Also, would it be better to but up my motherboard to 16x in order to use the full benefits of my VGA? I am not planning on running to VGA's for a while.
what happens is this. your given 16 lanes on the pci express bus. when you run in sli its splits BOTH your slots into 8 lanes each. so there is a bottle neck in when compared to a mobo running two full 16x slots. now that said, a 7900gs, doesn't max out a 8x slot...now an 8800gtx thats another story. my guess is your problem is something else. virus, malware, spyware, or even windows bloatware. do a fresh system boot. go to your task manager. see how much ram is in use. if your in 300-500+ meg range. that could be your problem. if your under that run ur virus scanner and spy/malware remover and see if you find something. what are your system specs btw?
What is your motherboard? some SLI systems keep the single graphics card running at X16 until you add the second, then they both run at X8 unless they are the "special" high end ones with too many lanes to count.
your certainly in the scenerio i described early spliting your lanes up. and again its not enough to bottle neck a couple of 7900gs boards. i ran two 7800gtx's (which out perfom and take more bandwidth than yours) and benched just fine but with the 8800gtx i got, i knew better than wasting money on a second one cause i like you spilt 8x lanes and the 8800 series was the first to max out the 8x lanes (that i know of, happy to learn if someone knows better). i adopted sli before there was any such thing as two full 16x slots. yep you get to dig through software/ malware/ drivers....maybe even check your disk defragmentation. sorry bro, i hate doing things like that myself. time consuming...