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Why do fps drop in steps 60, 30, 15 etc
- Thread starter Mysterae_
- Start date
Simplest way to explain it tho not 100% accurate: when you lock vsync at 60Hz then the interval between each frame at the minimum is 16.66ms. When using VSync the screen will only render when a complete image is ready to be rendered so when the PC is capable of rendering at 60 or more fps there is always a complete new frame ready to be rendered. When the PC isn't capable of rendering fast enough to keep producing new frames at 60 or more fps then it re-uses the last frame and you have to wait an additional 16.66ms before it can start drawing a new frame if one is available.
So if your only churning out 50fps you get 2x 16.66m gaps between new frames being rendered 1000ms (1 second) divided by 33.32 = 30 frames per second. If there still isn't a new frame ready you have to wait an additional 16.66ms which means 1000/49.98ms = 20fps and so on.
So if your only churning out 50fps you get 2x 16.66m gaps between new frames being rendered 1000ms (1 second) divided by 33.32 = 30 frames per second. If there still isn't a new frame ready you have to wait an additional 16.66ms which means 1000/49.98ms = 20fps and so on.
Thanks Rroff, I think I get it. When you say the pc isn't capable of rendering, you mean the gpu? What if the gpu usage isn't 100% but something like 60% when the drops ocurr? I'm not entirely sure (I'll check it in a minute with Afterburner) when my frames drop from 60 to 45 then 30, my gpu usage isn't 100%, more like 55 - 60%.
I'll go see if I can get it to do it again and post an image of the Afterburner trace.
I'll go see if I can get it to do it again and post an image of the Afterburner trace.
Depends on the whole PC - the CPU as well as the GPU are involved in building the next frame to render so if the PC as a whole can't produce a new frame in time for the next new frame to start rendering it will cause a drop in the actual rendered fps and increased input latency.
This is why most new games use triple buffering with vsync, rendering a third frame allows to counter these issues.
On the other hand, it introduces an input lag.
I really don't understand this 
Sometimes in the odd game I see this behavour, locked at 60fps then down to 30fps, back up to 60fps. But in the main I just don't see it.
Playing batman AC for example I see my fps going from a steady 60 down to 55, 49, 58 etc, I don't have triple buffering enabled in the Nvidia CP and I do have vsync enabled.
Any ideas?
Sometimes in the odd game I see this behavour, locked at 60fps then down to 30fps, back up to 60fps. But in the main I just don't see it.
Playing batman AC for example I see my fps going from a steady 60 down to 55, 49, 58 etc, I don't have triple buffering enabled in the Nvidia CP and I do have vsync enabled.
Any ideas?
Yep, vsync is satan.
Remove it
Ignore this. Tearing is satan. Keep Vsync. Lesser of two evils.
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Both are satan. FPS limiting is where it's atNo point going over 60 FPS if your screen is only capable of 60hz.
Probably a daft question, but how do you limit fps without using vsync?
is there some 3rd party software i need?
Yes afterburner does it, also latest Nvidia drivers with adaptive vsync
MSI Afterburner (and any software based on it) or Nvidia Control Panel/nvidia Inspector.
Adaptive vsync uses vsync to cap fps at your refresh rate so it's not a relevant answer.
I really don't understand this
Sometimes in the odd game I see this behavour, locked at 60fps then down to 30fps, back up to 60fps. But in the main I just don't see it.
Playing batman AC for example I see my fps going from a steady 60 down to 55, 49, 58 etc, I don't have triple buffering enabled in the Nvidia CP and I do have vsync enabled.
Any ideas?
Like I said, most games have triple buffering implemented by default nowadays.
I agree, tearing is terrible!
I can understand the fps dropping low when the gpu can't keep up, but not when it's only being used 50%, that's not efficient. I'll post the traces that show this pretty clearly when I get back from work.
I didn't know Afterburner had a vsync option, where is it? I'll need to try that out instead of in game and nvidia cp.
I can understand the fps dropping low when the gpu can't keep up, but not when it's only being used 50%, that's not efficient. I'll post the traces that show this pretty clearly when I get back from work.
I didn't know Afterburner had a vsync option, where is it? I'll need to try that out instead of in game and nvidia cp.
What version of nvidia drivers is this in (can't remember what I'm running) and is it enable by default? It could be this giving grief?
For starters, the game could be CPU-limited in those scenarios. Or you simple have a driver issue. Or there's another bottleneck somewhere that causes the sudden loss in fps.
Vsync doesn't have a vsync option, where did you read this?
There's no difference between using FPS limiter in Afterburner or drivers. And yes, it will still cause tearing because it's not vsync.
300+ drivers. It's not enable by default and you clearly don't understand how it works since it has nothing to do with your issue.
Moreover, if you've read through my posts in this thread, you'd get your answer. Lack of triple buffering when vsync is on causes that.
/thread
Definetly not cpu limited, (i7 2600k @ 4.4) nowhere near max utilisation or thermal limit, infact only 45C. It could be that damn PCIE Revodrive SSD hogging the PCIE bus but since nothings loading or saving I don't think so. Incidently the vram loaded is only 600mb of the 570's 1.2gb. I'm starting to think it's the game badly optimised.
I think you mean Afterburner? straxusii mentioned it earlier in the thread.
Vsync doesn't cause tearing, we know that....
No, I clearly don't understand what is happening in my instance because I asked this forum. Smart ass.
Have we got to the root of the problem? No. Thanks for your help and everything, but until I've got a reason and hopefuly a solution to the problem it still exists and is not resolved.
So it's not your CPU, do a clean install of drivers and make sure that some caching isn't in the works that could slow down your system for a while.
Yes, I meant Afterburner, and no, straxusii didn't say anything about MSI Afterburner having an option for enabling vsync.
That's not what I said. You're confusing Vertical Synchronization and FPS Limiter, both do different things and have different outcomes. Limiting FPS to or below the refresh rate will still cause tearing (albeit reduce it by a fair margin) and that's the only option you will find in Afterburner.
That and you also didn't understand what I've written.
Jumps from 60-45-30-15 are caused by Vertical Synchronization with double buffering, it has been explained by Rroff and me in this thread. Unless there's another underlying issue that causes it, that's your problem and it's easy to fix with something like D3DOverrider or nvidia Inspector tool.
This is going nowhere since you don't take anyone's response in this thread seriously.
Try running D3DOverrider (enable Force Vsync and Triple Buffering) with the game that is causing those fps fluctuations and see if that resolves the problem. Then try turning Vsync off entirely, even force it off on the drivers level, see if the GPU usage changes dramatically. Then, if the previous two testing methods fail, do a clean drivers install. Then look for other bottlenecks.
Also, read my posts carefully, if you don't understand something clearly, ask, I'll be glad to help, but don't make assumptions that you know what you're talking about when you really don't (like replying to my post regarding Afterburner and fps limiter, when you're confusing it with vsync, etc.).
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Adaptive Vsync doesn't get rid of all the tearing though.
