I have found some issues with gta4's own vsync setting, at least using my GTX 295. It doesn't behave like other games vsync control where they normally ask the gfx card to control the vsync.
Instead vsync in GTA4 seems to simply reduce the maximum frame rate to below the refresh rate of the screen. For example on my HDTV, at 50hz, using GTA4's vsync control, my fps maxes out about 45fps (seen with fraps).
This of course gives a slight judder every second or so rather than perfect 50fps vsync. I also notice in strenuous areas of Liberty City, using GTA 4's own vsync control, the frame rate is much lower than when using the gfx cards own vsync control.
For this reason, I decide to set force vsync on in the nvidia control panel, and vsync off in gta 4. This allows me perfect 50fps in areas that arn't very detailed, and gives me higher, and smoother frame rates in detailed areas of the city, if only by a few frames per second.
The only problem with disabling vsync within gta4's options, is instead of taking 10-15 seconds to load the city, it takes 5-10 minutes to load the city. So I think rockstar should address both of these issues.
1) Vsync On: GTA4 should do proper vsync like other games, not simply reduce the frame rate to make it be lower than the refresh rate.
2) Vsync Off: GTA4 shouldn't take a lifetime to load with vsync set to off.
Edited by mark007, 21 May 2010 - 11:32 AM.