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On 9/5/2018 at 1:22 PM, Colonel X said:

That is false information. Using "vsync locked at 1/2 refresh rate" setting, frames will drop below 30 to whatever you're capable of running, there is no "switch" to 15 FPS.

That's not entirely correct. See https://hardforum.com/threads/how-vsync-works-and-why-people-loathe-it.928593/ and http://www.tweakguides.com/Graphics_9.html for some good explanations of how vsync works. To quote from the text in the first link, when using standard vsync "the framerate can only be equal to a discrete set of values equal to Refresh / N where N is some positive integer. That means if you're talking about 60Hz refresh rate, the only framerates you can get are 60, 30, 20, 15, 12, 10, etc". This also applies if you're using vsync 1/2 refresh rate - it won't just run at some arbitrary intermediate framerate.

Where it becomes different is if you're using adaptive or adaptive 1/2 refresh rate. With those settings, vsync will only be enabled whenever the framerate exceeds the monitor's refresh rate (or 1/2 of it, as appropriate), so you could then run at some random lower framerate but with the possibility of some tearing.

Edited by vortex681

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On 5/7/2018 at 4:23 PM, vortex681 said:

If you use the standard vsync, it "locks" (synchronises) your framerates to the monitor refresh rate. However, using a 60Hz monitor as an example, if your framerates drop below 60, vsync then "locks" them to 30. If your framerates fall below 30, vsync continues to drop them using fractions of the monitor's refresh rate (30, 20, 15 and so on).

That is, again, false information here. Using regular VSYNC will limit your FPS to 60 in case your FPS exceed that limit. It will not lock to 30, 15 or anything else. Using it in X-Plane, you probably won't notice it's on, because you will probably never exceed 60 FPS and thus the "lock" will never kick in. Using VSYNC "half refresh rate" will limit to 30 (and again, not to 15 or anything else).

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2 hours ago, Colonel X said:

That is, again, false information here. Using regular VSYNC will limit your FPS to 60 in case your FPS exceed that limit. It will not lock to 30, 15 or anything else. Using it in X-Plane, you probably won't notice it's on, because you will probably never exceed 60 FPS and thus the "lock" will never kick in. Using VSYNC "half refresh rate" will limit to 30 (and again, not to 15 or anything else).

You're correct if you use adaptive vsync (or adaptive 1/2 refresh rate vsync) but not if you use standard vsync (or standard 1/2 refresh rate vsync). The whole point of vsync is to prevent screen tearing by delivering whole frames from the frame buffer, synchronised with the refresh rate and this can only be done at either the monitor's refresh rate or at some directly divisible fraction of it. With standard vsync and a 60Hz monitor, the game may be producing 75fps but only 60fps are being sent to the monitor. If your in-game framerate subsequently drops to 50fps, only 30fps are actually being sent to the monitor (one every second monitor refresh cycle) so that the monitor continues to get whole, synchronised frames to display. Unlike adaptive vsync, standard vsync continues to operate below the monitor's refresh rate so has to limit the number of frames per second sent to the monitor so that they remain synchronised with the refresh rate. 

Please see my most recent post above (10 Sep) for some links which describe the process much better than I can. 

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You really shouldn’t make claims based on stuff you read (particular on some forum from some guy who thinks he figured something out from reading some other stuff on some other forums) which you may not fully understand yourself.

I use vsync, and before building my current machine, dropped below 30 all the time and never ever reached 60, and my frame rates were NEVER some fraction of 60. Using several frame rate counters, the rates varied across the spectrum. The counters count the actual FPS of the screen refreshes. Even though they count averages rather than each individual frame, the result would be closer to the fraction integer.  My frame rates were frequently in the mid-20s for extended period. In my new machine, FPS is often locked at 60, but when it drops below that, it doesn’t drop to 30. It ranges through the 40s-50s.  

There is no “in-game” frame rate separate from the actual frame rate of the monitor. 

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37 minutes ago, Griphos said:

You really shouldn’t make claims based on stuff you read

Other than watching a video (and there are some good ones explaining vsync) it's difficult to know how else you'd get the knowledge. Because I had a lot of problems with screen tearing in the past, I read into it extensively (from actual books!). I only linked those explanations because they describe the process well and it saves me having to repeat much of it.

41 minutes ago, Griphos said:

There is no “in-game” frame rate separate from the actual frame rate of the monitor.

There is if it's less than the refresh rate and you're not using vsync (or you use adaptive vsync).

Whilst I can't argue with your figures, I can argue confidently about how standard vsync works. Unless the graphics card can send a whole frame to the monitor every time it refreshes, then you'll get tearing to some extent. That's where vsync comes in. If you have a 60Hz monitor and get 40FPS from the game (33% slower than the refresh rate) every time the monitor updates the screen, the video card can only draw 2/3 of the next frame leaving 1/3 of the previous frame which will make the image look torn. Vsync delays the next screen update until a whole frame can be drawn so, in this case, it would have to wait for a further monitor refresh cycle - that is 2 cycles for a single frame to be drawn so effectively 30FPS. It can't be a higher FPS as that would be out of synch with the refresh rate and would, again, produce tearing.

Adaptive vsync doesn't have this problem as it only works if your framerates are above the refresh rate, in which case it then limits your FPS to the refresh rate. Once your framerates drop below your refresh rate, adaptive vsync turns off allowing whatever framerate you have to be displayed (but with the possibility of tearing).

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1 hour ago, Griphos said:

You really shouldn’t make claims based on stuff you read (particular on some forum from some guy who thinks he figured something out from reading some other stuff on some other forums) which you may not fully understand yourself.

I use vsync, and before building my current machine, dropped below 30 all the time and never ever reached 60, and my frame rates were NEVER some fraction of 60. Using several frame rate counters, the rates varied across the spectrum. The counters count the actual FPS of the screen refreshes. Even though they count averages rather than each individual frame, the result would be closer to the fraction integer.  My frame rates were frequently in the mid-20s for extended period. In my new machine, FPS is often locked at 60, but when it drops below that, it doesn’t drop to 30. It ranges through the 40s-50s.  

There is no “in-game” frame rate separate from the actual frame rate of the monitor. 

Anyway, vortex681's claims are well informed claims, because it's exactly how it works on my computer. If I check vsync in X-Plane's graphic options, the frame rate is always a fraction of my monitor's refresh rate (Linux here, but I could check on my window machine). Now, if like ColonelX you tweak Nvidia parameters, (for example using adaptative vsync), your mileage may vary.

Pascal

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I'm referring to knowledge that comes from actually working in the industry.  If you don't have that, and you are just reading things, then you shouldn't pretend you know what is going on just because you read someone say something.

I DON'T work in the industry, but I can tell you from experience with standard vsync that my FPS are not some divisor of the refresh rate like 30 or 15.  Perhaps this works differently somehow with Linux, as Pascal suggests, but with Windows, it just doesn't work this way.  Or at least it never has with ANY of the hundreds of games and sims I have played across several different Windows machines.  

If your computer can output 40 FPS, and you have standard vsync on, and your refresh rate is 60hz, then your computer will draw 40 FPS and your monitor will try to display 40 FPS.  It will stutter, because some of those frames will stay on the screen longer (several cycles) so that they can draw the next one without tearing, as you state.  Not every frame will stutter, because not every frame will take longer than a single cycle to draw.  The refresh rate sets a cap.  And you're right that for a given screen frame, vsync will insist it be drawn all at once, but you're wrong that this means a FPS of 30.  Some of the frames will be able to be drawn in a single cycle, and some not, and those that cannot be will take two cycles, and the resulting FPS showing on your monitor will be some average of the total, so anything in between 0 and 60 (or whatever your monitor refresh rate is) and stuttering, because of the uneven ability to draw without tearing.  

The real problem with vsync and a system not able to draw FPS at the refresh rate is stuttering, not FPS as a divisor of the refresh rate. 

Edited by Griphos
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10 hours ago, Griphos said:

If you don't have that, and you are just reading things, then you shouldn't pretend you know what is going on just because you read someone say something.

Straight from NVIDIA: https://www.geforce.co.uk/hardware/technology/adaptive-vsync/technology. I quote: " When frame rates dip below the cap VSync locks the frame rate to the nearest level, such as 45 or 30 frames per second. As performance improves the frame rate returns to 60". Although the article is notionally about adaptive vsync, it initially explains the problem with standard vsync. Is that authoritative enough for you?

Perhaps vsync isn't working correctly on your system (or you're using adaptive vsync).

Edited by vortex681

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I'm using normal vsync with the in game check box, and nVidia set to use the game setting (default).  In what you quote, it say locks to nearest level, and includes the possibility of 45. 45 is not half of 60. That alone disputes your earlier post. And nowhere does it say it does so in one second integer increments.  As I suggested, it is much more likely it does so only as long as needed, which essentially means on a frame by frame basis, which happens up to 60 times per second, leaving the average in any given second to fall anywhere along the integer line below 60, not locked at 30. 

But you didn’t just quote an authoritative source and let it speak for itself. You referenced an unauthoritative source and began making extrpolative (and simply wrong) claims about what happens on all our computers as if you yourself were an authority.  That’s the problem. Common on enthusist forums, to be sure.

if you’re still wanting to maintain your claims, why don’t you post a little video of you running XP with vsync enabled over demanding scenery and the internal frame counter showing you locked at 30 FPS because you can’t reach 60. Just the game vsync. Not nVidia. And not set to cap at 30, but at 60. In other words, showing that vsync set to run at the refresh rate of 60 hz but unable to do so actually drops you to locked 30 FPS. 

Or, short of that, please explain why every YouTube video of XP out there with the frame counter showing actually shows FPS all over the place anywhere from 20s up to 60 FPS. If you were actually right, no video would ever show FPS at anything other than 60, 30, or 15. Neither you nor I have ever seen that. 

Edited by Griphos

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8 hours ago, Griphos said:

But you didn’t just quote an authoritative source and let it speak for itself. You referenced an unauthoritative source and began making extrpolative (and simply wrong) claims about what happens on all our computers as if you yourself were an authority.  That’s the problem. Common on enthusist forums, to be sure

I didn't claim to be an authority, I just repeated what I've learned from those who I consider to be much more informed than you and I and whose expertise I trust. I have not made "extrpolative" claims, I've just quoted sources who know much more about how vsync works than either of us do. Since you clearly will not even accept information from NVIDIA, who actually make the hardware and firmware that most of us use, I see no point in continuing this discussion. Please consider this to be my final post in this thread.

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