A couple of times I've had the game all of a sudden begin stuttering a lot and it seems to persist until I restart ArmA from scratch.
It has happened three times: just when about to finish Showcase: Infantry, one time I don't remember quite how and finally just now as I was playing around on the same showcase and alt+tabbing and changing keybindings a lot but I would assume this happens more or less at random.
Video with stuttering:
http://www.youtube.com/watch?v=CZaUwhAG8-M
It's hard to see the stuttering perhaps but notice the framerate meter dipping from 40 to 20 and in other areas even dips down to 10-15 simply from turning around. When not turning around there is no issue whatsoever so it seems to be directly turning or possibly rendering related.
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Compare with this video after restarting the entire game, without stuttering:
http://www.youtube.com/watch?v=6ZUGFiPnY6I
See how smooth turning is by comparison?
My specs are:
Win 7 32-bit
GTX 560 Ti Hawk
Intel Core 2 Quad Q9550 @ 2.84 Ghz
4 GB RAM
So it’s a pretty standard gaming setup save for the somewhat weaker processor.
I’ve had this happen in several versions of the Alpha.