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SLi - Vsync - Input lag

Toadus

Toadus

Toadus

Associate
Joined
3 Apr 2009
Posts
151
Hey :)

I've noticed when playing COD4 or COD5 I get quite noticeable mouse / input lag when Vsync is enabled now that I'm SLi'ing 2 GTX 280's. Previously, Vsync didn't cause any real noticeable input lag, so now that I've enabled SLi, what gives? :confused:

Obviously turning off Vsync means no lag at all, but things don't look half as good. :(
 
Isn't there a setting in the NV panel that allows you to reduce the rendered frame delay? I believe its default setting is 3 frames of delay.

Will fire my rig up this evening (if i'm able) and check for you. :)

gt
 
I tried setting that option to 1, but it didn't make any difference. The fact that in only effects the game when Vsync is enabled is surely the key here?
 
Weird? :confused:

I don't have COD5 but with COD4 i get no lag at all - that's with full settings including V-Sync.

Drivers are 182.50 - which are you using?

gt
 
vsync has always caused input lag for me , you might not have noticed it with single card as the framerate without vsync wasnt high enough to cause much of a delay, with sli as the framerate is higher, its waiting longer to render the next frame which is causing the lag, e.g without sli you might be getting 70 fps which is only skipping 1 in 6 frames to make it 60, with sli in ideal conditions youll be getting 140fps which would be skipping just over 1 frame for every 1 displayed and thats whats causing the lag
 
RaiderX said:
vsync has always caused input lag for me , you might not have noticed it with single card as the framerate without vsync wasnt high enough to cause much of a delay, with sli as the framerate is higher, its waiting longer to render the next frame which is causing the lag, e.g without sli you might be getting 70 fps which is only skipping 1 in 6 frames to make it 60, with sli in ideal conditions youll be getting 140fps which would be skipping just over 1 frame for every 1 displayed and thats whats causing the lag
Click to expand...

I wasn't aware that was how Vsync worked, very interesting!

You may not be aware of this, but you can set the maximum framerate for COD4 within the console system. The command is: /com_maxfps xx Where 'xx' is the framerate. By default, it's set to 85. If your theory is correct, then I could set this command to, say, 70, then enable Vsync, and the input lag should be less. I'll give this a whirl, but I've got a feeling I may have tried this already as I was playing about with it yesterday. By the way, with this max FPS setting on no limit, I noticed there were some areas were I was getting over 350fps, LOL. :eek:
 
Actually, I've answered my own question here...

By default, the max FPS is 85, as per the console command, so when I've been getting the input lag with Vsync enabled, the game would not be allowing more than 85 FPS anyway. So if I manually restrict it to 70 FPS, it's not going to make a blind bit of difference. Hmmm, the mystery continues. I'm guessing Vsync and SLi may have a slight compatibility issue.

GT-Junkie - Are you POSITIVE you don't get ANY input / mouse lag with Vsync enabled? Try turning Vsync off, and see if the cursor movement feels any different?
 
Last edited:
gt_junkie said:
Will double check but i've never had any issues - always felt pretty sharp to me.

Framerates are:

Min: 78
Avg: 120
Max: 245

gt
Click to expand...

Thanks for looking into this.

I found the most obvious way to notice the input lag is: Set up a multiplayer game of your own, in the menu where you get to choose your character, i.e, just before the match starts, move the mouse around, and it feels horrid! All sluggish like it's too slow.
 
If you set the fps high enough you should make the tearing pretty much unnoticeable except on areas with a lot of parallel lines like blinds and radiators. You will need atleast com_maxfps 125 and a min fps of 100 for this to work.

No decent fps player should ever use vsync online.
 
Seriously? I couldn't tell the difference from 70fps to 300fps. It all looked shocking... With Vsync enabled, it looks lovely and fresh and smooth, just laggy! :(
 
I have never found VSync + SLI to work together but I've always found VSync to induce a rubber band effect even with a single card.

Thats why I have always gone for SLI systems as personally with a constant 100+ fps it all looks smooth and nice again for me.

Have you tried changing the tripple buffer setting? also playing with the r_swapinterval and r_finish commands ingame? (I think COD has them)
 
Ooo, never heard of those COD commands. Can you explain more? :)

Tripple buffering is meant to increase performance when Vsync is enabled, but it's is also meant to cause lag. Also, tripple buffering is not supported in Direct3D games yet, only OpenGL. You can force tripple buffering with certain app tools, but it's actually meant to make lag worse, so I haven't bothered... :)
 
I was getting very bad input lag with my 4870x2. But after playing about with various settings it turned out to be caused by Vista mouse acceleration! :o

Turned it off and then it worked perfectly. :)
 
r_swapinterval is basically the internal VSync on/off command - 1 being on.
r_finish 1 supposedly reduces input lag when using VSync.
 
Overslop said:
I was getting very bad input lag with my 4870x2. But after playing about with various settings it turned out to be caused by Vista mouse acceleration! :o

Turned it off and then it worked perfectly. :)
Click to expand...

I only get it with Vsync on, so it can't be mouse settings... :)
 
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