vsync frame limiting, is this true?

[hat]

Saw this in an article about adaptive vsync:

The problem with turning VSync on is that the framerate is locked to multiples of 60. If the framerate drops even just a little below 60 FPS VSync will drop all the way from 60 FPS to 30 FPS. This is a huge drop in framerate, and that large change in framerate becomes noticeable to the gamer. The result is called stuttering, and when you are playing a game that consistently changes between only 30 and 60 FPS, the game speeds up and slows down and you feel this difference and it distracts from the gameplay experience. What's worse is that if the framerate drops ever so slightly below 30 FPS the next step down for VSync is 20 FPS, and then the next step down is 15 FPS.

I'm not quite sure whether to believe this or not. I've been gaming with vsync on for many a year and I never saw framerates drop from 60 straight down to 30. I never felt such a drop, and I never saw anything like that any of the times I used a tool that showed me what my current framerate was. I didn't always have powerful hardware either... I gamed on a damn 8500gt for a while with vsync on, you'd think if this were true about vsync my framerate would have been tripping over itself all over the place.

[sneekypeet]

I would assume its plausible, but even then I would think it to be card and game specific (as in not all cards and all games react in the same way).

[Aquinus]

VSync implementations vary between video cards, their vendors, and the software being used. Dead Space used to cap at 30 FPS with vsync on even though my card could do 90 without vsync on (at the time.) Have you tried setting the application to "VSync off" and using nVidia drivers to force VSync on to see if the driver-level setting has any difference?

[W1zzard]

the quote from hardocp is completely correct and applies to all hardware based vsync mechanisms.

basically the card waits for a flag from the display output logic "image redraw complete", and then sends the next frame. if it misses it due to longer rendering time it has to wait until the next "complete" which is one frame later (1/60th + 1/60th = 30 FPS). if it misses that too it has to wait again (1/60th + 1/60th + 1/60th = 20 FPS)

[LAN_deRf_HA]

This is why I play with vsync off on all but really old games. Huge performance hit most of the time. It's damn near useless. I tried that new thing from nvidia in inspector where you just set a cap but you still get tearing.

[Aquinus]

Originally Posted by LAN_deRf_HA

I tried that new thing from nvidia in inspector where you just set a cap but you still get tearing.

IIRC that is because without vsync, frames are written directly to the framebuffer where vsync is active it is loaded and buffered into the framebuffer then it is displayed. VSync should only impact performance if you're rig isn't handling the game well to begin with. Any machine that does 60fps+ should show improved image quality and smooth gameplay from VSync being activated (not to say >60 FPS isn't smoother (@60hz that is) but you also won't run your machine over your refresh rate so you really can't see it.). I also never noticed the 20, 30, 60 fps issue with my 6870 in or out of crossfire. As for crossfire, I don't drop below 60 FPS and I find that micro-stutter is less noticeable with vsync on.

[entropy13]

Originally Posted by LAN_deRf_HA

This is why I play with vsync off on all but really old games. Huge performance hit most of the time. It's damn near useless. I tried that new thing from nvidia in inspector where you just set a cap but you still get tearing.

You set a frame cap (Common - Frame Rate Limiter - On), but you aren't using Adaptive Vsync (Common - Vertical Sync Tear Control - Adaptive), and of course turning on Vertical Sync in the first place (Common - Vertical Sync - Force On)?