It happens for me with or without Vsync. However, if I have Vsync on, my FPS is constantly going back and forth between 59 and 60. Every couple of seconds, especially when exploring a level for the first time, I experience a "tic" or a snag, it's as if the frames are getting caught for a millisecond and then suddenly catching up so that it looks like the game is skipping a frame or two.
In Source games, when this snag happens, I notice that my FPS, for a split second, shows a number somewhere in the 100's.
It's most apparent when using the mouse to look around, but it also happens when strafing or moving in general. It will also happen if I use the keyboard to look. I have tried this with both USB and PS/2 keyboards and mice.
My video card is a Sapphire 3850 AGP. I've tried every Catalyst driver I can find and none of them help. I'm almost certain that when I first got the card a month ago, I was not having this problem.
I have tried reinstalling Windows, I have tried removing other devices. Nothing I do seems to make any difference.
P4 3.0 GHz
2 GB DDR400
800 Mhz FSB
I know I don't have the fastest machine but I was able to play Source engine games for five years on this rig with a 6800 GT and I have never had this problem until now.
Valve updates the Source Engine with every new Source game, so L4D's Source would be better than HL2's.
What Source games are you playing? L4D(2) is very CPU-intensive, when hordes/mobs attack the CPU can be too slow.
The problem is actually worse in older source games.
It almost never happens in L4D. It happens only a little on L4D2. It happens A LOT in CS:Source and HL2 Deathmatch.
It's not a low-FPS problem from CPU load in times of high combat. I can start up a completely empty level in CSS with no bots and I get this skipping problem all over the place. It becomes less frequent as I explore the level, but even in previously unexplored levels the snagging still happens.
Again, the most unusual aspect of it is the same split second in which the hitch occurs, the FPS shoots up into the 100s (even though Vsync is supposed to keep it at 60).
Also, as I said before, when I first got the card about a month ago, I was not experiencing this problem. I'd tried various drivers and I'd noticed that L4D2 was especially choppy during FPS transitions, but I'd somehow found a driver that smoothed them out. I'm almost certain it was the 9.10s, but now no driver set I try gets me back to smooth gameplay.
Also, if I use limit the FPS in CSS by using fps_max to 60 or below, I no longer get the snagging (unless I'm moving into an area of the map where the FPS tends to drop). So it seems to me that the jerking that I'm getting is a very unsmooth FPS transition of some sort.
Why on earth Vsync would allow the FPS to jump into the 100s I have no idea, but again, I'm also convinced that I've had setups with smoother framerate changes.
For instance, when I first installed the 3850, I could play Far Cry 2 on all low settings and no problems. Now, the framerate is slightly unstable and if I look around, I get a LOT of jumping and skipping. Funny thing, when I went back to my 6800GT, I saw the same thing.
Three years ago I bought a new system and upgraded it 3 times now.
No matter which setup I used the problem was always there.
This were/are the specs:
GIGABYTE P35C-DS3R to ASUS P5E PRO X48
CORE 2 DUO E6420@2,13 to E8500@3,8 oc (30c stable)
7950GT to HD4850 to GTX275
DDR2-1066 to DDR3-1333 to DDR3-1600
600WATT power supply
It's the most noticable on 3dmark Vantage & Anno 1404
If it put Vantage on the lowest details, the problem is still occur!
It's not really a BIG problem, more annoying sometimes.
But a program like Vantage needs to be run smoothly.
I have a perfect "GPU" benchmark of 11500 with the GTX275
But still annoying to see the frame skipping!!!
I know I have a pretty fine pc I run every game on the highest settings very smoothly.
Modern Warefare 2 & Crysis I almost see no frame skippings. Glad!!
Maybe the skipping occur due to some programs running on the background. But I had this with XP, Vista & Windows 7