Trouble with Vista/ Sli?

[clendn]

Hi, I just got a new computer with 2 Geforce 8600 Sli and a Quad Core Intel processor, with an Asus sli motherboard on Vista 64-bit. I couldn't help but notice that fps on games like Oblivion and Bioshock are less than I expected (still decent, but I expected seamless). I have a feeling that these games either do not support my configuration or I haven't properly installed drivers, tweaking, etc, even though I have made sure to download all the Vista 64-bit drivers.

(One more thing I noticed, after making sure Sli was enabled, there were the options for Sli performance mode: force split-frame rendering, force alternate frame rendering 1 and 2, and -- the default was "Single-GPU" wouldn't that imply that only one card is being used? This is why I think maybe I'm not doing something right.)

If anyone had some ideas or could shed some light for me I would greatly appreciate it.

Thanks,
John