Burdman27911 said:
IIRC it's the same thing as a CRT. My old CRT that I used to use would go up to 85hz (85 times per second) at full rez. My Dell widescreen lcd does 75hz. With both you will only be able to see up to that many frames per second, but your computer isn't limited to only producing that amount. You could have a game running at 205fps but you would only see 85fps at most. Vsync will make it look better (because it will be synchronized), but afaik it has less effect with LCDs than CRTs.
I'm sure people will have more info than I will, but that should give you a general answer.
My understanding is that LCD monitors don't have a refresh rate limitation in the same sense as CRT monitors. If your computer is spitting out 120 FPS in a game while Vsync is disabled, then the LCD monitor will *attempt* to draw each frame on the screen. The problem is that the response rate of LCD monitors is not sufficient to accurately reproduce the colors in each frame at such a high frame rate. The individual pixels cannot change color fast enough, so the result is a "ghosting" or "smearing" effect on the screen, where clarity is lost.
For this reason, LCD manufacturers set a recommended "refresh rate", so that these effects are minimized. For an LCD monitor that comes with a "refresh rate" of 60 Hz (such as the Dell 2005FPW), the computer will only be outputting 60 frames per second in the Windows environment. In games, it is recommended that Vsync be enabled to limit the frame rate output to the Windows default--60 Hz in this case. At 60 Hz, each pixel should be able to accurately produce colors corresponding to each frame outputted by the computer.
So, to directly answer your questions:
No, you don't *HAVE* to cap your FPS using Vsync, but it is recommended that you do so, especially if you are sensitive to the motion blur issue described above. Some people are really bothered by "ghosting", while others don't seem to notice as much.
You can also cap your FPS in many games by using console commands or editing your config file. I notice you mention 76 and 125 FPS, so I assume you play games based on the Q3 engine. In such games, you can cap your FPS by typing "/set max_fps 76" in the console or in your config file. Rather than play with Vsync on, you may find that capping FPS at 76 is acceptable to you.
I hope this helps.