Has Fast Sync similar results to G-Sync?

[Hans Power]

I just got Mass Effect Andromeda and suffice it to say it's not running brilliantly with my GTX 960 4GB. I get about 30-45 FPS on average, very rarely hitting 60.

Now I deactivated V-Sync ingame and activated Fast Sync instead via the Nvidia Control panel and while the FPS number stays the same, the difference in smoothness and input lag (or the lag thereoff) is like NIGHT AND DAY. The game runs much smoother and there is no mouse lag anymore - much nicer gameplay experience. Now I wonder if Fast Sync has a similar end result than G-Sync because G-Sync is supposed to have the same effect on paper. Unfortunately I never had the opportunity to try out G-Sync. Still, I'm interested - how different are the end results concerning framerate smoothness and input lag? And to make things clear I'M NOT INTERESTED IN TECHNICAL DIFFERENCES! I'm well aware that Fast Sync works differently to G-Sync - I'm only interested in a practical comparison.

[Princess Luna]

Not exactly but Fast Sync is quite superior to the original v-sync... I use Fast Sync on my FreeSync monitor since I have nVidia and quite frankly when I tried a friend's rx480 I didn't really see any difference in smoothness... but then again I'm not exactly the most sensitive person on this department.

[Mira Yurizaki]

Fast sync will still cause tearing if the frame rate does not line up with the refresh rate. All fast sync does is cap the FPS to the refresh rate while allowing the GPU to render as fast as possible but throw on the last frame rendered.

[Hans Power]

1 minute ago, M.Yurizaki said:

Fast sync will still cause tearing if the frame rate does not line up with the refresh rate. All fast sync does is cap the FPS to the refresh rate while allowing the GPU to throw on the last frame rendered.

Sry to say but that's wrong, I don't get tearing with Fast Sync activated while I do if without V-Sync or Fast sync.

[Mira Yurizaki]

2 minutes ago, Hans Power said:

Sry to say but that's wrong, I don't get tearing with Fast Sync activated while I do if without V-Sync or Fast sync.

Ah wait, I got myself confused with what fast sync did.

 

Fast sync will limit your FPS like Vsync (so if you have 60 Hz, you're limited to 60 FPS, 30 FPS, 15 FPS, etc.), but still allows your GPU to render as fast as possible. There.

 

G-Sync allows for "any" arbitrary refresh rate and therefore, "any" arbitrary frame rate.

[Hans Power]

11 minutes ago, M.Yurizaki said:

Ah wait, I got myself confused with what fast sync did.

 

Fast sync will limit your FPS like Vsync (so if you have 60 Hz, you're limited to 60 FPS, 30 FPS, 15 FPS, etc.), but still allows your GPU to render as fast as possible. There.

 

G-Sync allows for "any" arbitrary refresh rate and therefore, "any" arbitrary frame rate.

No, actually that's not happening, either. Framerate in Mass Effect Andromeda (and other games which work with Fast Sync for that matter) is pretty much all over the place unless I limit it via Nvidia Inspector. On the first planet Eos I'm usually between 33 and 45 FPS, for example.

 

Edit: You just described the difference between V-Sync with Triple Buffering vs V-Sync with Double Buffering.

[ivan134]

37 minutes ago, Hans Power said:

I just got Mass Effect Andromeda and suffice it to say it's not running brilliantly with my GTX 960 4GB. I get about 30-45 FPS on average, very rarely hitting 60.

Now I deactivated V-Sync ingame and activated Fast Sync instead via the Nvidia Control panel and while the FPS number stays the same, the difference in smoothness and input lag (or the lag thereoff) is like NIGHT AND DAY. The game runs much smoother and there is no mouse lag anymore - much nicer gameplay experience. Now I wonder if Fast Sync has a similar end result than G-Sync because G-Sync is supposed to have the same effect on paper. Unfortunately I never had the opportunity to try out G-Sync. Still, I'm interested - how different are the end results concerning framerate smoothness and input lag? And to make things clear I'M NOT INTERESTED IN TECHNICAL DIFFERENCES! I'm well aware that Fast Sync works differently to G-Sync - I'm only interested in a practical comparison.

GSync and FreeSync are for screen tearing. The only thing fast sync has in common is that it will make gameplay smoother and more responsive. Fast Sync doesn't get rid of screen tearing.

[Frankenburger]

The benefit of GSync is that the monitor can match your GPU's output, which has a two fold effect of reducing stutter and eliminating tearing. Fast Sync merely updates the screen when there's a full frame, which eliminates tearing but because the GPU and display aren't technically matching, can still cause stutter.

 

There's actually a very in depth video done by Battle(non)sense if you want to learn more about the differences.

 

[Mira Yurizaki]

12 minutes ago, Hans Power said:

No, actually that's not happening, either. Framerate in Mass Effect Andromeda (and other games which worked with Fast Sync for that matter) is pretty much all over the place unless I limit it via Nvidia Inspector. On the first planet Eos I'm usually between 33 and 45 FPS.

Frame rate counters count how many times there was buffer swap. If we went by this:

 

Then what Fast Sync is doing letting the GPU render on the back buffer, turning that into the "Last rendered buffer" when done, and repeating the process. The front buffer is pointing to whatever the "last rendered buffer" is at the time of the next Vsync. So while an FPS counter may read out 45 FPS because it's counting how many times the back buffer and last rendered buffer swap, chances are you're only really seeing 30 FPS or something somewhat above it (however 1/45 seconds fits into 1/60 seconds).

 

The only to verify what the actual frame rate you're seeing is through something like FCAT or recording the monitor with a high-speed video recorder and doing careful frame-by-frame analysis.

[Hans Power]

Just now, ivan134 said:

GSync and FreeSync are for screen tearing. The only thing fast sync has in common is that it will make gameplay smoother and more responsive. Fast Sync doesn't get rid of screen tearing.

Sry, but that's also wrong. Fast Sync does get rid of screen tearing (cause I just did the direct comparison). You get smoother and more responsive gameplay WITH Screentearing with V-Sync OFF - no Fast Sync required for that.

[Shiv78]

Fast Sync eliminates most screen tearing but can still allow for stuttering. G-Sync eliminates both when within the monitor's range

[Mira Yurizaki]

Put it simply, Fast Sync is a driver implementation of triple buffering. Which I really should've just linked this article on my first post: http://www.anandtech.com/show/2794

[Frankenburger]

Just now, M.Yurizaki said:

Put it simply, Fast Sync is a driver implementation of triple buffering. Which I really should've just linked this article on my first post: http://www.anandtech.com/show/2794

To be more specific, triple buffered but decoupled to reduce input lag.

[ivan134]

16 minutes ago, Hans Power said:

Sry, but that's also wrong. Fast Sync does get rid of screen tearing (cause I just did the direct comparison). You get smoother and more responsive gameplay WITH Screentearing with V-Sync OFF - no Fast Sync required for that.

You are right. I keep forgetting what it does. It still adds latency so it's still not as good as GSync and only works when your framerate is above your monitor's refresh rate. So, it's still not as good as GSync or FreeSync.

[Hans Power]

3 minutes ago, Frankenburger said:

To be more specific, triple buffered but decoupled to reduce input lag.

Still looking a lot smoother than with V-Sync + Triple Buffering which is what I used before I tried Fast Sync in Mass Effect Andromeda and I'm almost ALWAYS below 60FPS.

[Frankenburger]

Just now, Hans Power said:

Still looking a lot smoother than with V-Sync + Triple Buffering which is what I used before I tried Fast Sync in Mass Effect Andromeda.

Mileage varies between setups. There are people who can't use Fast Sync because it causes stutter (my GTX 1060 laptop has this issue), while there are others who report more positive results. It seems to me that Nvidia has some ironing out to do on it, but Fast Sync has potential.

[Hans Power]

38 minutes ago, Frankenburger said:

Mileage varies between setups. There are people who can't use Fast Sync because it causes stutter (my GTX 1060 laptop has this issue), while there are others who report more positive results. It seems to me that Nvidia has some ironing out to do on it, but Fast Sync has potential.

I think, its more to do with the respective game (which is also true with G-or Free Sync). Many games just stutter if they reach a framerate between 30 and 60 or above 60FPS even with V-Sync off. Dunia Engine games (like Far Cry 3 and above) are tough to configure in that regard - they theoretically boast an open framerate but they still stutter with anything between 30 and 60 FPS (V-Sync off) if certain effects are on. I think it has to do with frametimes and how the engine handles it. Another interesting one is Shadow Warrior 2 which funnily produces smooth gameplay in between 30 & 60 FPS if V-Sync AND Triple buffering are on but stutters with V-Sync off OR Fast Sync on. I think it has to do with how the respective game engine handles the open the framerate. In the end the only way to reliably test how G-Sync/Free Sync compare to V-Sync with/without Triple Buffering to fast sync would be to test it with a game which features a truly open framerate (as in: NO microstuttering ANYWHERE above 30 FPS with V-Sync off) and measure the footage with a high speed camera as M.Yurizaki mentioned.

Btw. I play a lot of games (my Steam library has almost 500 games atm) and I noticed that games with a truly open framerate (as in NO microstuttering whatsoever w/o V-Sync) are in the minority.

 

Edit: I forgot - variations between setups could have something to do with the CPU, of course - those also affect frame times after all.

[jjohnthedon1]

1 hour ago, Hans Power said:

Still looking a lot smoother than with V-Sync + Triple Buffering which is what I used before I tried Fast Sync in Mass Effect Andromeda and I'm almost ALWAYS below 60FPS.

Placebo effect then because what you are describing is impossible 

[Hans Power]

Just now, jjohnthedon1 said:

Placebo effect then because what you are describing is impossible 

Nooo, way too noticable for that. I'm talking about the difference between runs like arse and runs really nicely. Also I haven't read or watched any indept analysis and/or actual benchmark of fast sync and reading this thread alone shows that it's not even remotely clear what fast sync actually does in actual practical application.

[jjohnthedon1]

27 minutes ago, Hans Power said:

Nooo, way too noticable for that. I'm talking about the difference between runs like arse and runs really nicely. Also I haven't read or watched any indept analysis and/or actual benchmark of fast sync and reading this thread alone shows that it's not even remotely clear what fast sync actually does in actual practical application.

Well first of all it doesn't activate untill u hit 60 fps so untill then you're just running vsync off

 

once over 60 the third buffer is de synced and the screen refreshes on a double buffer 

but the gpu is allowed to keep loading the third buffer which immediately replaces the back buffer once complete.

allowing for the most up to date frame rather than stalling the gpu for 16.6ms

 

 

 

 

[Hans Power]

6 hours ago, jjohnthedon1 said:

Well first of all it doesn't activate untill u hit 60 fps so untill then you're just running vsync off

 

once over 60 the third buffer is de synced and the screen refreshes on a double buffer 

but the gpu is allowed to keep loading the third buffer which immediately replaces the back buffer once complete.

allowing for the most up to date frame rather than stalling the gpu for 16.6ms

 

 

 

 

Doesn't quite explain why I don't experience any Screen Tearing below 60FPS despite V-Sync being off. Also it's not running in borderless window if you think it's because of that.

[Aur0ra12]

i've recently started playing ME:A as well, with a setup of gtx 1080 + 6700K + 3440x1440 ultrawide with 100hz native refresh rate.  in general my frame rate hovers around 60-80 on ultra with TXAA, and since my monitor comes with freesync, i had to find a software solution to the screen tearing -- and guess what?  fast sync works just as the OP described:  no capped fps, no screen tearing, with game play JUST AS SMOOTH as vsync off.

 

fast sync works the best when you've fps significantly higher than the monitor's native refresh rate, but in this case my guess is that it's working more like a modified implementation of triple buffering (without the limitation of having to turn vsync on) where only full frames rendered through the buffer sequence is used but the gpu is still allowed to render as many frame as it can to eliminate latency.