SLI = Double Framerate but stutters , solution ?

[jackcnd 0]

Here's picture proof that SLI can double framerates...

Left side SLI = 29 fps, right side single card =15.

 

Downside is SLI introduces high levels of stuttering in Flight and panning.

 

I read it being mentioned before, any solutions found since then,

or a newer GPU card needed?

 

 

Test: Appx 1300' over Honolulu looking towards airport,

with the sun low in the sky casting shadows.

Flight Preset at HIGH settings, 1920x1080, vSync on, 2700K@4.8

[dburne 2]

Hmm I did not think Flight was supposed to benefit from SLI...

 

I am not an SLI person, have never been or had any real desire to so cannot speak from experience, but have you tried playing around with vsync or an external frame rate limiter?

 

First I would try with both vsync off, and on, and see if either one reduces the stutter you are seeing. Alternatively, you can try limiting your fps with an external program - if you are familiar with Nvidia Inspector - the later Nvidia drivers included a frame rate limiter, and with Nvidia Inspector you can have access to that feature - I use it for FSX with good results.

[Guest]

Here's picture proof that SLI can double framerates...

Left side SLI = 29 fps, right side single card =15.

 

Downside is SLI introduces high levels of stuttering in Flight.

 

You say SLI doubles framerates but introduces stuttering. Could it be that Flight runs smoother at 15 fps without SLI then it does at 29 fps with SLI? In Flightsims fps doesn't really matter that much: smoothness is what matters. It's better to have a sort of smooth experience with an fps of 15 then a stuttering mesh with a useless 29 fps.

 

Flight is smooth on my computer and I haven't got a clue what the fps is. (I am glad MS removed the fps counter from the game ). Try not to focus too much on fps, focus on smoothness!

 

I guess the best solution is getting a newer GPU without bothering with SLI. But that's my take on it: I never had an SLI system, mainly because FSX couldn't handle it.

[jackcnd 0]

Thanks for the replies, I will tinker with the settings.

 

Jeroen your right smoothness is key :), but once fps slips below 15 even in Flight I notice it's lacking.

 

If anyone wants to try this simple benchmark, I put the Flight save files online here:

http://members.shaw....ht/Free Flight/

 

Should be able to copy them to your Documents/Flight/Shared/Free Flight directory load the saved flight.

Can check framerate with Fraps running. Here's the demo version of Fraps:

http://www.fraps.com/download.php

 

Just trying to make the right choice of a new card, if needed.

Maybe if others have a minute to report results

we can see just how the different cards perform in Flight.

[funk420 0]

Well I run with SLI on my PC (2 x GTX 260) and I've tested Flight and it definitely does make a difference. I used to occasionally get some stutters, especially when there are lots of trees loaded on the screen, but they seem to have mostly gone away. I also run with VSYNC on, which has actually made the graphics a lot smoother for me.

 

I did notice that you mentioned it is choppy when panning, in which case it might have to do with the repeat settings. If you check the standard.xml file, which contains your controller settings (found in "C:\Users\"YOU"\AppData\Local\Microsoft\Flight\Players\"SOME NUMBER"\Career\Controls"), consider changing the repeat rate for the PAN_VIEW section of your controller (the section might be in the file a few times if you have multiple controllers) to match this:

 

<Down>

<EventName>PAN_VIEW</EventName>

<EventUnits>meter</EventUnits>

<Repeat>1.000000</Repeat>

</Down>

[DMagick 0]

I use SLI in Flight and I definitely see an improvement, but I haven't really noticed any difference in stuttering with SLI on vs. off.

 

From what I've heard though, this is a common problem with SLI/Crossfire. I think the issue is that one card is processing a frame faster than the other. It's sometimes easier to think of the framerate in seconds per frame instead of frames per second (25 frames per second is the same as 40 millisecond per frame). So if one card is finishing a frame in 20ms the other might be taking 60ms. You would still see 25 frames per second, but there would be a noticeable stutter.

 

I think this is something that can be improved with new drivers, but I haven't seen any information about improvements to SLI in Flight from the latest Nvidia drivers. As someone mentioned earlier Nvidia Inspector can be used to tinker around with settings in more detail than what the normal control panel uses. A google search for 'microstuttering and SLI' might give you some help, but I think issues related to this are specific to each game.

[RYR738 9]

Flight, just like FSX does not take advantage of SLI or Crossfire.

That is straight from the dev team.

Sli is strictly a GPU driver thing and sometimes causes more problems with than without.

 

Fred.

[jackcnd 0]

nVidia Inspector's frame rate limiter does help, also the vsync setting.

 

Flight may not have been coded with SLI in mind but SLI doubles my frame rate!

 

Watching cpuz and inspectors GPU usage graphs, Flight behaves very different from FSX.

Flight seldom pushes the CPU to 100%, most of the time it runs well below max frequency,

whereas FSX is the opposite.

 

Flight does peg the GPU at 80-100% , whereas FSX sits around 30%.

 

So it seems more GPU horsepower will help Flight.

More CPU power will help FSX.

 

Be interesting to see what framerate other cards give in this senario...

[Heimi 91]

Indeed interesting, I have a solid 60fps all the time with a single card. Is this the top end?

[ZATZAi 0]

I don't have SLI however I plan to get it relatively soon and have been doing a lot of research on it. The problem you're having sounds like Micro-stutter, a problem specific to SLI and Crossfire setups where the graphics cards and Monitor refresh rates fall out of sync because the FPS of the graphics cards are a number that is too high or too low compared to the refresh rate (ie 60hz or 120hz) of the monitor and the number is not easily divisible. The standard solution to this problem as I have read is to enable VSYNC, so that your graphics cards lock in at an FPS equivalent to your monitor's refresh rates (Assuming they can), so 60FPS for a 60hz monitor, and no higher. 60FPS is where micro-stutter is supposed to go away, or start to go away, if your FPS is lower like 30FPS it may feel like only 15-20FPS, so reducing graphics quality may be required at that point.

 

Dual card GPUs like the 590 also suffer from this same phenomenom. Another option, interestingly, is to add a third graphics card and that apparently reduces microstutter as it changes up the timings (Four cards works too but it's not as big an improvement as moving from 2 to 3 cards). I've also heard it said that running multiple monitors can reduce microstutter if each monitor is handled by it's own video card, I don't know how true this is though as it depends on how SLI/Crossfire handles the rendering of all the screens.

 

There's an excellent write up on Tom's Hardware here: http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html

[dburne 2]

Indeed interesting, I have a solid 60fps all the time with a single card. Is this the top end?

 

It is if you are running with vsync on , ie the max fps is equal to your monitor's refresh rate...

[jackcnd 0]

ZATZAi - thanks for the detailed reply, will read the link.

 

Heimi - What card are you using?

If you get the chance, try the scenario I posted about , love to hear your results.

Use the saved flight or a time when the sun is creating shadows on the buildings. Those are impacting my framerate by 20% +.

 

Be great to find a solution for constant 60fps on High :)

[ZATZAi 0]

ZATZAi - thanks for the detailed reply, will read the link.

 

Heimi - What card are you using?

If you get the chance, try the scenario I posted about , love to hear your results.

Use the saved flight or a time when the sun is creating shadows on the buildings. Those are impacting my framerate by 20% +.

 

Be great to find a solution for constant 60fps on High :)

 

My system currently uses a Geforce 275 which is very close to a single 280 in performance. Today I am upgrading to a 560 Ti 448 (The 448 part is very important, the regular 560 Ti is noticeably slower) which has performance similar to a 570. It may be a worthwhile upgrade from a 280 as you could get two of them relatively cheap (They're prices are dropping as the 600 series is coming out now). I got mine for around $230. I'll report back on what the performance is like with my single 560 Ti 448.

 

Also keep in mind some settings in flight don't look any better on High than they do on Medium, like Shadows etc. Someone did a post on that here earlier.

[ZATZAi 0]

Just to report back on what I said for anyone interested. I'm getting 30-60 FPS with the 560 Ti 448 depending on how busy the scenery is where I am with mostly high/max settings on a single 1920x1080 monitor.