FPS vs Monitor Refresh Rate

[beep]

Can some knowledgeable person explain what limits, if any, Monitor refresh rates (e.g. 60 Hz) have on FPS? Can FPS ever exceed monitor refresh rates in the "real world"?

Does 100FPS really mean anything if my image can only refresh at the monitor rate?

[=Sarc=]

There's a term called image tearing that occurs when FPS exceeds the monitors refresh rate. Think of two frames that are slightly different but you see the top half of one and the bottom half of the other. Some may be really bothered by this and turn on an option called v-sync. This locks the FPS to the refresh rate but your FPS has to be higher than your refresh rate to stay in sync (ie. you can't turn on v-sync to make 30 FPS turn into 60 FPS to match a monitor's 60 Hz).

Getting 100 FPS is still important because it you to turn on v-sync (I think it's more noticeable on LCD monitors) and keep smooth framerates. It's still the same without v-sync. The higher the FPS, the smoother game play will be.

[beep]

Originally Posted by =Sarc=

There's a term called image tearing that occurs when FPS exceeds the monitors refresh rate. Think of two frames that are slightly different but you see the top half of one and the bottom half of the other. Some may be really bothered by this and turn on an option called v-sync. This locks the FPS to the refresh rate but your FPS has to be higher than your refresh rate to stay in sync (ie. you can't turn on v-sync to make 30 FPS turn into 60 FPS to match a monitor's 60 Hz).

Getting 100 FPS is still important because it you to turn on v-sync (I think it's more noticeable on LCD monitors) and keep smooth framerates. It's still the same without v-sync. The higher the FPS, the smoother game play will be.

Makes sense...thanks, Sarc.

[Lorian]

You should note that using vsync can slow the frame rate more than it should, it creates a short gap between rendering each frame to keep it synced, so having 100fps normally is important for keeping it at 60 when using vsync.

[beep]

I'm not quite sure what my frame rates will be with my new system (Conroe E6600 with 2 Gig RAM and a single Asus nVidia 7900GTX to drive a Dell 20" (1600x1200) monitor), but they will be far better than my existing 4 year old system where 60 FPS is "high", 20-25 FPS is "normal" and 2-6 FPS is a common occurence when the screen is busy.

[Lorian]

I have a 6800XT and have all my settings on high and most of the time I'm at around 30fps, so I only get tearing when I'm looking at the sky really. It shouldn't be much of a problem.

[=Sarc=]

Originally Posted by beep

I'm not quite sure what my frame rates will be with my new system (Conroe E6600 with 2 Gig RAM and a single Asus nVidia 7900GTX to drive a Dell 20" (1600x1200) monitor), but they will be far better than my existing 4 year old system where 60 FPS is "high", 20-25 FPS is "normal" and 2-6 FPS is a common occurence when the screen is busy.

I think it should do well for the most part. The GTX has 512MB RAM that will help with a high resolution. It might not guarantee >60FPS but you should stay above it for most of the time in a lot of games. You really can't get any hardware better than that unless you get a GX2 or go SLI. I say don't worry because you'll enjoy the new system for sure.

[beep]

Here's some other stuff I found on the topic...

FPS vs. Refresh Rate

As previously mentioned, FPS and refresh rate are two separate things. Even if the image on your screen has not changed in any way (e.g. a still 2D image like your Windows Desktop), or your 3D game isn't actually supplying enough new frames (e.g. the game is running at 25 FPS on a 60Hz refresh rate), the screen is still being redrawn a fixed number of times based on the current refresh rate of the monitor; if your FPS is less than your refresh rate at any time, some frames may simply be redrawn several times by the monitor.

However if your FPS is higher than your refresh rate at any time, your monitor will not actually be able to display all of these frames, and some will come out with a graphical glitch known as Tearing. To prevent this, you can enable an option called Vertical Synchronization (VSync). However here's the tricky part: if VSync is enabled, then your refresh rate and FPS will actually have a relationship to each other - they will become synchronized together, and your FPS may even fall a great deal overall. This is all covered in more detail in the Vertical Synchronization setting.

and

FPS & VSync

When VSync is disabled, your FPS and refresh rate have no relationship to each other as such. This lets your graphics card work as fast as it wants, sending frames to the monitor as fast as it can draw them. Whether the monitor can actually show all these frames properly or not is another matter, which we've already discussed above. Clearly if disabling VSync can cause graphical glitches, however minor they may be, wouldn't it make sense to always enable VSync so that your graphics card doesn't wind up wasting its efforts only to generate more tearing? Well once again, things are not as simple as that.

When VSync is enabled, what happens is that your graphics card is told to wait for your monitor to signal when it's ready for a new frame before supplying a single whole frame, each and every time. It can't race ahead, it can't just pump out lots of partially completed frames over old ones whenever it's ready - it has to provide a single whole frame to the monitor whenever the monitor says it's ready to refresh itself during VBI. The first noticeable impact is that your FPS becomes capped at a maximum equal to your current refresh rate. So if your refresh rate is 60Hz for example, your framerate can now only reach a maximum of 60FPS. By itself this isn't really a problem, since every monitor can do at least a 60Hz refresh rate at any resolution, and as we've discussed under the Frames Per Second setting, if your system can produce 60FPS consistently in a game this should be more than enough FPS to provide smooth natural motion for virtually any type of game.

There is however a more fundamental problem with enabling VSync, and that is it can significantly reduce your overall framerate, often dropping your FPS to exactly 50% of the refresh rate. This is a difficult concept to explain, but it just has to do with timing. As we know, when VSync is enabled, your graphics card pretty much becomes a slave to your monitor. If at any time your FPS falls just below your refresh rate, each frame starts taking your graphics card longer to draw than the time it takes for your monitor to refresh itself. So every 2nd refresh, your graphics card just misses completing a new whole frame in time. This means that both its primary and secondary frame buffers are filled, it has nowhere to put any new information, so it has to sit idle and wait for the next refresh to come around before it can unload its recently completed frame, and start work on a new one in the newly cleared secondary buffer. This results in exactly half the framerate of the refresh rate whenever your FPS falls below the refresh rate.

As long as your graphics card can always render a frame faster than your monitor can refresh itself, enabling VSync will not reduce your average framerate. All that will happen is that your FPS will be capped to a maximum equivalent to the refresh rate. But since most monitors refresh at 60Hz or above, and in most recent games it is difficult to achieve 60FPS consistently at your desired resolution and settings, enabling VSync usually ends up reducing your FPS. Fortunately, because this problem is pretty much caused by the frame buffers becoming filled up, there is a solution and that's to enable a third frame buffer to allow more headroom. However this is not a straightforward solution, and to read more about this see the Triple Buffering setting.

So Which is Best, VSync On or Off?

VSync poses a real dilemma for many people: with VSync off, tearing can occur whenever your graphics card and monitor go out of sync, and this can be very annoying for some people, especially in fast motion games. However with VSync on, your FPS can often fall by up to 50%. This can be resolved on many systems using Triple Buffering, but that also brings with it a range of possible problems. So which choice is right for you?

Well clearly I can't give you a one-size-fits-all answer, but I can provide some suggestions. To start with, I strongly recommend setting VSync to 'Application Preference' in your graphics card's control panel. This is because ideally you should set your VSync preference on a game-by-game basis, preferably using the in-game settings, as the choice will differ depending on the type of game you are playing. Newer games with complex graphics for example will be different to older games which your system can run much more easily. Remember, in games where your FPS is consistently above your refresh rate, enabling VSync is perfectly fine and results in no real drop in FPS.

In general, I recommend starting off with VSync disabled in any game as this is the most trouble-free method of gaining the fastest possible performance. This is the simplest solution, and on monitors which have lower refresh rates, or for games in which your framerate is not very high, this appears to be the best solution. You may notice some tearing, but this will generally be minimal if your FPS remains below your refresh rate anyway. Remember though that even if your FPS matches your refresh rate exactly, or is even below it, whenever VSync is disabled the graphics card and monitor are not strictly in sync, and tearing (however minor) can occur at any time.

In any game if you find tearing annoying, you should enable VSync. If you find your FPS has halved, you should then specifically try enabling Triple Buffering, as this can help fix the FPS drops related to enabling VSync, but it introduces the possibility of hitching on graphics cards with less VRAM, and possible control lag on some systems. See the Triple Buffering setting below for details.

There is no clear choice for everyone when it comes to VSync, and this is why the option to enable or disable VSync exists both in the graphics card control panel and in games. As long as you understand what it does however, you can make an educated choice to suit your hardware and tastes.

[RandomGuy]

I have never seen "tearing" happen on any combination of video card, monitor and game. I say turn off vsync and don't worry about it until you see a problem.

[beep]

Originally Posted by RandomGuy

I have never seen "tearing" happen on any combination of video card, monitor and game. I say turn off vsync and don't worry about it until you see a problem.

That's exactly what I'm doing.