Huge framerate disparity xp vs vista

[psyphon]

I'm running Grid on xp64 & vista 64 with the following system specs:

q6600 (stock speed)
780i
4GB RAM
8800 gtx sli (stock speed)
drivers and bios are current (175.16 xp, 175.19 vista)

with the following in-game graphic settings:

1920x1200
4xaa
ultra when available

my problem is lower framerates in Vista, only on the night time courses.
For example, in the first race of the highest, non-global, gt1 race in the japanese class i get between 22 and 27 fps. But in xp i get around 47 fps.

I've unistalled the game, tested it with no patch, patch 1.1 and patch 1.2, and there has been no improvement.

any help appreciated.

[psyphon]

Okay, i disabled SLI in the Nvidia control panel and my frame rate increased to a level comparable to the numbers i was getting in xp. The geforce drivers i'm using in xp, despite being the most recent released, do not seem to run in SLI mode while playing Grid. While the Vista drivers (175.19) do, indeed, have a SLI profile for Grid.

The only change i've made to the driver profile was switching from the "multiple-display mode" to the "single-display mode." Thus, the "sli render mode" remains "Nvidia recommended" status.

Any idea why i would get lower frame rates on night courses while using SLI in vista, but clock higher overall frame rate averages on daytime courses?

side note: i've patched to 1.2 and it seems to have fixed the "stutter" i was getting in-game. No longer need to set the cpu priority to "high."

[WhiteSnake]

The Game doesnt even suport SLI, and by default SLI wont work.

You need to set "Alternate Frame Rendering 2" to get SLI to work for the game.

You can simply check if a game uses SLI or not by selecting "Show SLI Visual Indicators" as show in the picture, if nothing apears and you see no SLI logo the game doesnt use SLI and simply runs on one card only.

http://i47.photobucket.com/albums/f173/RS_Patrick/SLI.jpg

TIP: You can test the best Alternate SLI Rendering setting by using FRAPS and the SLI indicators to see wich way you get the most FPS out of it.
Just mesure the same bit of a game everytime with a difrent setting and see if you get more or less FPS.

[psyphon]

Thanks for the reply.

As far as SLI is concerned, it has been my experience that SLI is, indeed, working in Vista, but, sadly, not in Xp (64-bit versions of both os.)
Not only were my average frame rates much higher in Vista (except, of course, during the night races) but the temperatures on both my cards were relatively the same. Were as in Xp, my frame rates had an overall lower average and there was a significant disparity in card temps, leading me to conclude that only a single card was being worked.

I know for sure that there is a SLI profile in the newest nvidia vista-64 drivers (175.19). I've not checked for one in xp.

Thanks for the hint as far as the "AFR 2" goes. I will give it a try.