Sorry rusty but that is not absolute.
I remember exceeding the Vram on single 3870 512MB in Race Driver Grid, on a single card @ 2560x1600 when the game first came out, it was less than 1 FPS on some settings and that was just on the menu screen.
When i added CF the FPS jumped to 25fps, when i added a 3rd GPU the FPS jumped to 70fps and the only reason why the scaling went like that is because every added card was giving the other card/cards more time to Refresh the Vram before its turn came up, but even that has limitations because when doing the 24 hour race as it got darker and darker the fps drops steadily as the Vram requirements got even higher until it stopped at 30fps.
So i added a 4th GPU my fps went to 90fps but as i got to the 24 hour race as it got darker and darker the fps drops steadily again as the Vram requirements got further and further past what i had until it stopped at 30fps again.
I just dropped 1 setting one notch in the game menu and even a single card would do 45fps avg.
If i had 3-4 way GPU from the offset i would not have been any the wiser that Vram was the cause and could have assumed it was just that the game needs more grunt than what i had when it came to the 24 hour race at night.
Now DMC3 again when i exceeding the Vram on some parts of the game it would stutter slightly, more GPUs gave me more fps but it would not stop the stuttering until i dropped the AA one notch, but no issues with cards with more Vram.
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