I recently reinstalled the game after some time off, and are experiencing some fairly horrendeous microstutter.
The game usually runs normally for a while; then, at some point - usually around the ten minute mark - the FPS drops with around 10 (It usually goes from the 50s to the 40s.), and microstutter starts setting in.
I haven't been able to find any particular common denominators as to what causes this - it appears that it sometimes happens upon entering a vehicle. Also, I had one experience where the game ran fine until I died, and upon respawning, the microstutter was there. These might of course be coincidences.
I run the game at 1920x1080 resolution, with everything maxed-out and VSync disabled. When the microstutter isn't there, the game usually runs at around 50-60 FPS, which I find fine for the most part.
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My computer.
Two "NVIDIA GeForce GTX TITAN Z"s in SLI.
32GB RAM.
"Intel Core i7-3960X".
64-BIT "Windows 7 Ultimate".
The game runs from a regular, non-SSD harddrive.
All other games run fine, I have all the latest drivers and the latest Windows-update. I have tried verifying the game cache.