Could be a couple of things. Drivers to start with. I don't think Stalker is
very well optimized. Before the last patch, Someone had made a demo to run
to get benchmarks and I ran them under XP, Vista32 and Vista64. Both vista32
and Vista64 ran the demo about 20 fps slower than XP did. Which at the high
settings took the average from 74 to 54. I found watching the demos that
Vista had alot more stutters and hangs than XP
I have an ATI card and with the 7.2s and 7.3s ATI is getting pretty darn
close to the same performance in some games. FEAR being the closest, with
only about a 5fps difference. Doom3 (an OPenGL game) the worst, with about a
15-20 fps difference. The 3dMark06 scores are less than100 points different.
Funny enough, I think the head bobbing is worse under XP, then Vista. So
while Vista stutters more, I don't get as dizzy playing it.
But the Short answer to your question, is that, Most games play just as good
under Vista64, as they do under Vista32. Stalker is just a bad game on Vista
at the moment, they are suppose to be release a Vista patch, which hopefully
they will clean up the code a little. Maybe ATI and Nvidia need to tweak
their drivers more for Stalker
