If a game maxes out the vram on your gpu, you can still run it. the vram is not combined, it is mirrored in both CF and SLI. From what i have experienced, running out of vram does not necessarily kill your fps everytime you run out of it. Crysis at enthusiast settings @ 1680x1050 use all of the vram (512mb) on my 9800gtx's. The game would normally use about ~870mb, if i had enough vram from what ive seen. I still get decent fps in the low 40s and sometimes high 30s. If i set the textures to low, and tweak all the everything to reduce memory usage, it doesn't really add much performance. Its not really until you start to add AA that you will see big drops in performance if you don't have the vram. Also, i played nfs: hot pursuit 2010, and it used all of my vram at max settings, but i still got a buttery smooth 60fps (with vsync on).
However, you will experience more stuttering and random fps drops in-game if you have no vram left. crysis uses at least 900mb of vram at 1920x1050 as you can see in this thread http://www.overclock.net/graphics-ca...-you-need.html
. The gtx 560's will definately run out of vram at 5760x1080, but still manage to pull 24 fps average as you can see in the corner of the monitorEdited by Brian123 - 1/26/11 at 5:26pm