XP Video Memory?

[1st.Gunnery]

Hey all,

i have some problems on the end of a round, it looks like my vRam getting to full and slowing down my FPS.

Im always starting with nice FPS rates, but after some time i take a look at my Vram useage displayed by Rivatuner and it tells me it is useing more than 600mb of it. Well there is still more than 200mb left, but why do i get so bad FPS??

IG settings:

1920x1080 via shortcut
Terrain - Medium
Effects - Medium
Geometry - High
Texture - High
Lighing - Medium
Dy Shadows - Off
Dy Light - Medium
Anti Alaising - 4x
Texture Filtering - High
View - 100%
+Widescreen fixer

Is it normal that PR sucks so much vRam?

System specs:

WinXP Pro x64
M3N-HT Deluxe
Phenom II 940
8GB CL4 RAM
GTX 260 - 896mb
23,6" FullHD Monitor