To use SLI or not to use SLI, that is the question

[Billy Pilgrim]

Sorry about the predictable Shakespeare parody title for this thread. Couldn't resist.

I'm about to start building a pc, specifically for racing sims, and especially for AC and pCARS.

I'll be using a triple-monitor setup.

Please tell me, what is better for running Assetto Corsa: one GPU or two? I know that some sims run better with one GPU rather than two, but what about AC?

I'm hesitating between getting a GTX 780ti or two 780s

If you know anything about pCARS regarding SLI, I'm all ears.

(First post here - yeeah!)

 

[Martymcfly]

Hi everyone
I got totally addicted to this game from the first moment I played. And after 100 hours or so of playing...
One thing I noticed personally with this game is that my CPU usage hits 100% on one of my 3770K cores while the other 7 cores rarely reaches 20 - 30% usage. My GTX Titan average usage is between 65 and 90% and I never see it reach a 100% wall like I do on my CPU core. My specs are
3770K @ 4.6 / GTX Titan with a slight OC / 16 gig ram @ 2400 / SSD Vertex 4 / I play at 2560 1440 res. everything maxed out except my AA is at 4x and fast AA is at 1.

I don't think having 2 or 3 Titans or 2 680's will help us staying above 60 fps when our CPU are reaching 100% on one core and barely using other cores.
I can't wait to see the graphic improvements this Friday...

 

[RaceNut]

Hi everyone
I got totally addicted to this game from the first moment I played. And after 100 hours or so of playing...
One thing I noticed personally with this game is that my CPU usage hits 100% on one of my 3770K cores while the other 7 cores rarely reaches 20 - 30% usage. My GTX Titan average usage is between 65 and 90% and I never see it reach a 100% wall like I do on my CPU core. My specs are
3770K @ 4.6 / GTX Titan with a slight OC / 16 gig ram @ 2400 / SSD Vertex 4 / I play at 2560 1440 res. everything maxed out except my AA is at 4x and fast AA is at 1.

I don't think having 2 or 3 Titans or 2 680's will help us staying above 60 fps when our CPU are reaching 100% on one core and barely using other cores.
I can't wait to see the graphic improvements this Friday...

That is supposed to be one of the big advantages to DX12, it will be able to spread the load very evenly across all cores.

 

[Leemstradamus]

Hi everyone
I got totally addicted to this game from the first moment I played. And after 100 hours or so of playing...
One thing I noticed personally with this game is that my CPU usage hits 100% on one of my 3770K cores while the other 7 cores rarely reaches 20 - 30% usage. My GTX Titan average usage is between 65 and 90% and I never see it reach a 100% wall like I do on my CPU core. My specs are
3770K @ 4.6 / GTX Titan with a slight OC / 16 gig ram @ 2400 / SSD Vertex 4 / I play at 2560 1440 res. everything maxed out except my AA is at 4x and fast AA is at 1.

I don't think having 2 or 3 Titans or 2 680's will help us staying above 60 fps when our CPU are reaching 100% on one core and barely using other cores.
I can't wait to see the graphic improvements this Friday...

My cpu usage seems to be a little more balanced than yours. One core is high, and I only seen the 95% once when the Nurburgring GP came out. I'll look at it some more when I get home.

 

[RaceNut]

Another thing I have noticed with AC, if I use more than 10 or 11 AI - I would have some micro-stutters. When I tested with 23 AI, the stutters remained as did the same FPS. I tried doing 2 things to alleviate the stutters:

• Apply the in-game FPS cap to about 70
• Change the "Pre-render Frames" in my Nvidia control panel settings I don't recall what default is but, I went from 1 to 2 PRF

Both of these things seemed to help to eliminate the issue but, I found it curious that there was no difference in the number of AI used and I do get the 95% CPU warning quite often.

PC: Intel i7-4770 CPU /// GeForce GTX 670 @1920x1080 single monitor /// 16GB RAM

 

[Leemstradamus]

Another thing I have noticed with AC, if I use more than 10 or 11 AI - I would have some micro-stutters. When I tested with 23 AI, the stutters remained as did the same FPS. I tried doing 2 things to alleviate the stutters:

• Apply the in-game FPS cap to about 70
• Change the "Pre-render Frames" in my Nvidia control panel settings I don't recall what default is but, I went from 1 to 2 PRF

Both of these things seemed to help to eliminate the issue but, I found it curious that there was no difference in the number of AI used and I do get the 95% CPU warning quite often.

PC: Intel i7-4770 CPU /// GeForce GTX 670 @1920x1080 single monitor /// 16GB RAM

Which tracks and how many AI are you running when you get the 95% warning? Also what speed is your cpu at?

 

[RaceNut]

Which tracks and how many AI are you running when you get the 95% warning? Also what speed is your cpu at?

I don't think the track matters, I haven't tested that specifically but, I get the warning every-time I play. The number of AI doesn't matter either, I think it will show up even running in practice mode alone. My CPU is stock. I suspect there is something else triggering the warning but, no other issues and no FPS problems either after solving the stutters.

 

[Jan-Olov Johansson]

Strange with so many different results on this subject, as I mentioned in some other thread: I never get the cpu warning unless i turn down my gfx settings from max...then it comes. (with a full grid that is)

 

[Leemstradamus]

It is strange. What OS you running @RaceNut? I never get that message but only a handful of times and then it never came back. Also what on screen apps are you running?

 

[RaceNut]

It is strange. What OS you running @RaceNut? I never get that message but only a handful of times and then it never came back. Also what on screen apps are you running?

Win7 HomePremium, only apps are for Pedals, track map if learning a new track, maybe one other - I'll have to check. I'll try turning those off and see if it changes anything.

 

[Leemstradamus]

Try hiding the overlay ctrl+H

 

[Martymcfly]

Another thing I have noticed with AC, if I use more than 10 or 11 AI - I would have some micro-stutters. When I tested with 23 AI, the stutters remained as did the same FPS. I tried doing 2 things to alleviate the stutters:

• Apply the in-game FPS cap to about 70
• Change the "Pre-render Frames" in my Nvidia control panel settings I don't recall what default is but, I went from 1 to 2 PRF

Both of these things seemed to help to eliminate the issue but, I found it curious that there was no difference in the number of AI used and I do get the 95% CPU warning quite often.

PC: Intel i7-4770 CPU /// GeForce GTX 670 @1920x1080 single monitor /// 16GB RAM

Hey RaceNut
Your GTX 670 should have just enough horsepower to run @ 1920x1080. Try to OC your 4770 a bit and see if you get a little more smoother experience and more consistent 70 fps.
I recently upgraded to 8.1 Pro but when i was using Win 7 premium I had manually changed my CPU cores to unparked to reduce stuttering in some games..
In my situation I just wish I didnt see my 3770K core hit 100% usage. I'm pretty sure that is causing my dips below 60fps and not my Titan.
And you're right it doesn't matter weather its hot lapping in monza or racing against 11 AI in Monza, one core on the CPU always hits the 99% usage mark quite often.

 

[RaceNut]

Try hiding the overlay ctrl+H

I'll try that - thanks Saleem.

 

[RaceNut]

Hey RaceNut
Your GTX 670 should have just enough horsepower to run @ 1920x1080. Try to OC your 4770 a bit and see if you get a little more smoother experience and more consistent 70 fps.
I recently upgraded to 8.1 Pro but when i was using Win 7 premium I had manually changed my CPU cores to unparked to reduce stuttering in some games..
In my situation I just wish I didnt see my 3770K core hit 100% usage. I'm pretty sure that is causing my dips below 60fps and not my Titan.
And you're right it doesn't matter weather its hot lapping in monza or racing against 11 AI in Monza, one core on the CPU always hits the 99% usage mark quite often.

AC runs butter smooth capped at 70 FPS - never fluctuates other than the first corner with a full grid of bumper cars.

 

[Pedro Cunha]

I have two 680's and get better performance than you, which shouldn't happen! Your system has an issue. We have been through this. If you now have three then you should still get even larger performance. Something is wrong with your system.

Saying that the game is broken, when everyone else says contrary should let you know to check out what else could be wrong.

show me a video of 1 lap at Monza maxed out 1080p, back of Lotus125 full grid not droping from 60fps!!!!

when i say maxed out, i mean every single video option activated and maxed out!

show it to me

 

[Leemstradamus]

I think you are getting confused? Where did anyone say that they run it maxed out?

Frankly, trying to help you is giving me a headache.

 

[Pedro Cunha]

I think you are getting confused? Where did anyone say that they run it maxed out?

Frankly, trying to help you is giving me a headache.

I was replying to this "Martcerv" guy who said:

"...I only have a single 2560x1440 screen but can max it out with a full field of AI and get solid frames above my refresh rate..."

 

[Pedro Cunha]

This is 16 AI grid Totaly maxed out game with Titan SLI. Never droping from 60fps no matter what.

Saleem, yes the game is broken because i drop from 60fps to 22fps when switching from 16 to 17 AI grid.

 

[Martymcfly]

Yes GSC 2013 works very well with SLI maxed out with regular ingame AI and all works great though the game itself is only single threaded so its CPU bound with lots of AI. I think you could likely max everything out with a single Titan but you can even run 64x SLI AA with 16x SS and it has zero effect on frame rates due to it being CPU bound.

I just tried it again and checked the OSD and actually got better frames earlier but think I had HT off then which benefits single threaded apps, actually benefits anything running 3 or less threads on my i7 2700@4.8ghz.

Getting 84fps at 2560x1440 maxed back of grid at Interlagos in mini's and 260fps on my own. GPU load with AI drops quite a bit as the CPU single thread is the bottleneck with GPU load even at those settings down quite low with lots of AI. I tool some screen grabs but for some reason cant post them here, I will reboot and turn off HT to see what the performance diffrence is.

Hey Martcerv

My cpu usage seems to be a little more balanced than yours. One core is high, and I only seen the 95% once when the Nurburgring GP came out. I'll look at it some more when I get home.

My cpu usage seems to be a little more balanced than yours. One core is high, and I only seen the 95% once when the Nurburgring GP came out. I'll look at it some more when I get home.

Hi Saleem
Try special event Classic Run in Lotus Type 49. ( Simple Race no AI )
My first core CPU usage is spiking to 99% usage all the time. Which results in slow downs as I race. The trees around me slow down and the whole game experience stutters and my frames drop from 60... The rest of my cores are under 20 to 40% of usage and my GPU GTX Titan barely reaches 85% at times...

 

[RaceNut]

Try hiding the overlay ctrl+H

Saleem - thanks buddy, that did the trick.

 

[martcerv]

show me a video of 1 lap at Monza maxed out 1080p, back of Lotus125 full grid not droping from 60fps!!!!

when i say maxed out, i mean every single video option activated and maxed out!

show it to me

The lotus 125 are very sketchy so this wouldnt be possible as all their collisions will slow things down as collisions are pretty badly done in AC atm, any car the AI can drive ok I have been able to keep it above or locked to 60fps maxed out.

Obviously If i try and record a video this is not goint to happen as it kills the framerate pretty badly. Also when I was using the onscreen apps this was having quite a big negative effect on fps especially in a large field. Turning all these off changes the frame rates greatly and I have confirmed this checking the FPS graph data after races.

Here is an older video only 16 cars but having lots of onscreen apps that I have found to cost about 20 to 30 fps since plus recording with shadowplay that costs about another 20-40% and settings weren't fully maxed. I think cube res medium and not sure about motion blur but I rarely use it so most likely it was off but it looks a bit blurred.

Its capped at 60 and there is a slight slowdown at the start here but without the extra load of recording and apps which have been confirmed by the AC devs in my post here.

http://www.assettocorsa.net/forum/index.php?threads/apps-performance-impact-a-bit-high.7835/

Running maxed out with a full field needs apps off and no frame recording as this will cut the frame rate in half at these high loads. The frame rate dropped to below 60 with no apps briefly but I have also since tested with Motion Blur, max smoke, max and cube high with no effect on min FPS just the max stays a bit lower. Also the tests in the above linked thread had HT on which lowers my min FPS turning it off gets more solid performance and my CPU can run easily at 5ghz that way but only 4.8 with HT on.

The main thing is AC is quite CPU limited and with 2x titans OC and 5ghz OC on the cpu without the slowdown of the apps when in SLI, when the CPU bottlenecks the GPU's usage is down to 30 or so each completely maxing it out still doesn't get them into full usage with lots of AI on screen and so I get pretty much the same min frame rates with min GFX setting or maxed out gfx settings.