View Full Version : SLI + Vsync

05-17-06, 03:03 PM
Does SLI still suffer from using vsync? I had a couple of 7800's and ended up selling them and going ATI due to the frustration i dealt with in reguards to wanting to run vsync. It either didn't work right at all, or you suffered wierd performance/smoothness issues. Just wondering if all that was cleared up or not.

05-17-06, 03:06 PM
From what I understand, Vsync works on games that use AFR...

The Bigman
05-18-06, 12:45 AM
Im curious as well. I had this issue with FarCry. Enabling Vsync dropped the FarCry Performance alot i mean 30 fps. I don't know what it does to SLI but if i set it to Application controled, i get real bad tearing in U2k4. and FarCry runs clock work.

We need this topic to become a sticky so that its at the forfront of this forum.

Its a very good topic. Can others elaberate on these issues with Vsync and SLI?

05-18-06, 03:51 AM
If you enable vsync then you also should consider turning on triple-buffering or you will suffer a huge framehit. Check fps and you'll see your framerate jump from 60fps down to 30fps, 15fps and back up again when the screens are busy. Fps is constrained to discrete rates (granularity) which are integer divisors of screen refresh rate (60/1 60/2 60/3 60/4 etc) and fps jumps around between those values too all the time when vsync is enabled - makes for jerkiness in complex scenes.

05-18-06, 07:25 AM
In the notes for the 84.43 official beta driver, it states support for vsync in SLI. Anyone try these to see if there is a performance hit?

05-18-06, 07:41 AM
i have been running COD2 with vsync on, and tripple buffering forced and it works. currently using 84.21

05-21-06, 11:50 AM
Below are some results from FEAR that I posted in the dxtweaker thread (this is without using dxtweaker). It looks like it's working fine to me although this game does use AFR. I guess I'll see if I can find a game that uses SFR and test that.

41/41/57 (0/0/100)

FEAR+SLI+Vsync Off
53/81/267 (0/0/100)

FEAR+Single GPU+Vsync On
19/32/59 (7/73/20)

FEAR+Single GPU+Vysnc Off
26/42/81 (0/60/40)

MaxPayne 2 uses SFR but the results aren't very conclusive. For one, SLI doesn't seem to help much in general so it's hard to tell if anything is making a difference. I had to use fraps and I was using the 7th Serpent mod. I basically started it and just stood there until they killed me. They sometimes killed me quicker than others and I didn't always fall the same so bear that in mind when looking at the results (i.e. it's a rough estimate). Guess I'll look for another SFR game to test.

MaxPayne2 (SLI+vsync off)
Avg: 62.452 - Min: 51 - Max: 115

MaxPayne2 (SLI+vsync on)
Avg: 53.410 - Min: 45 - Max: 61

MaxPayne2 (SLI+vsync on+in-game TB)
Avg: 52.497 - Min: 39 - Max: 61

MaxPayne2 (Single GPU+vsync on+in-game TB)
Avg: 55.035 - Min: 38 - Max: 61

MaxPayne2 (single gpu+vsync on)
Avg: 52.879 - Min: 35 - Max: 62

MaxPayne2 (single gpu+vsync off)
Avg: 62.140 - Min: 42 - Max: 105

The Bigman
05-21-06, 02:44 PM
I did some simular tests with F.E.A.R and got the same kind of results not numbers but with Vsync. What a differences Vsync makes. Does AFR2 do any better with you?

05-21-06, 06:53 PM
its going max 60fps becouse its lcd refresh rate.