Bottleneck....680 sli

Skynet5 · 15 Apr 2012 at 18:38

Hello,

Have very fast cards, 3 year old 1st gen i7 920 (stepping c) at 3.9.

BF3 running at max (minus motion blur), this is a nice scene pulling around c.85 fps:

By laurencenoton at 2012-04-15

If I drop 4xAA to 0xAA I can get that green line to follow the CPU almost bang on, this results in no noticable increase in fps.... but I guess there is something in it, all I see is my GPU usage go down. GPU usage runs around 70-89% and CPU at around 85%.

So this shows a GPU bottleneck? Obviously that doesnt sound right. Any ideas? If my CPU is a bottleneck why does it process frames quicker than my GFX can? SLI is definitly enabled by the way.

Concerned that I'll update my mobo and chip and not really see any difference.

I'm getting roughly 80-100fps on average, with lows of 56 very very rarely when about as much happens as possible...Die Hard scene type stuff.

nutsnut · 15 Apr 2012 at 19:09

sorry for the hijack, what developer code was used to show that graph?

TallPaul_S · 15 Apr 2012 at 19:12

nutsnut said:
sorry for the hijack, what developer code was used to show that graph?

Its the first line in the command line in the screenshot he posted, "Render.PerfOverlayVisible 1"

Freddie1980 · 15 Apr 2012 at 19:25

I'm sure things will improve with future drivers the cards are brand new don't forget so drivers are not vey mature.

TallPaul_S · 15 Apr 2012 at 19:31

For the graph, it just means your FPS is limited by your GPU's, if you had a CPU bottleneck the yellow line would be above the green, meaning that the CPU was rendering frames slower than the GPU, thus limiting the FPS.

andybird123 · 15 Apr 2012 at 19:37

what motherboard are you using? what are the PCI slots (e.g. 16x or 8x)?

as you're not hitting 100% CPU it's not a CPU bottle, but 8x pcie 2.0 causing an issue maybe?

Skynet5 · 15 Apr 2012 at 19:56

andybird123 said:
what motherboard are you using? what are the PCI slots (e.g. 16x or 8x)?

as you're not hitting 100% CPU it's not a CPU bottle, but 8x pcie 2.0 causing an issue maybe?

Hi, thanks for the interest.

The mobo is a P6T Deluxe V2. Within the control panel of Nvidia, looking at the system info, both lanes are x16. I believe that is correct for my mobo, I think it can support

16x 16x 1x
16x 8x 8x

Skynet5 · 15 Apr 2012 at 19:57

TallPaul_S said:
For the graph, it just means your FPS is limited by your GPU's, if you had a CPU bottleneck the yellow line would be above the green, meaning that the CPU was rendering frames slower than the GPU, thus limiting the FPS.

So we are down to thinking it is drivers that could potentially get me some more FPS.....

Wont be upgrading any time soon (4 day old baby upstairs!) but want to understand why Im getting what I'm getting. Happy as larry having SLI, certainly gives a boost on my setup.

tommybhoy · 15 Apr 2012 at 20:02

According to this thread, 2600K upwards is needed to remove the scaling bottleneck in 7970/680 dual card setups:

http://forums.overclockers.co.uk/showthread.php?t=18390360

But in your case it's quite a costly upgrade for a scant few fps more(probably only see a slight improvement in BF3) when it's probably running fine as it is anyway.

TallPaul_S · 15 Apr 2012 at 20:05

lnoton said:
So we are down to thinking it is drivers that could potentially get me some more FPS.....

Wont be upgrading any time soon (4 day old baby upstairs!) but want to understand why Im getting what I'm getting. Happy as larry having SLI, certainly gives a boost on my setup.

Actually, according to Repi (Dice dev), your graph is normal for SLI/Crossfire

https://twitter.com/#!/repi/statuses/129361863875104768

when SLI or Crossfire is enabled the green GPU line should be above the yellow CPU line

Skynet5 · 15 Apr 2012 at 21:00

TallPaul_S said:
Actually, according to Repi (Dice dev), your graph is normal for SLI/Crossfire

https://twitter.com/#!/repi/statuses/129361863875104768

Does this mean that I should see potential improvements as the drivers mature for the game/card?

Skynet5 · 15 Apr 2012 at 21:03

tommybhoy said:
According to this thread, 2600K upwards is needed to remove the scaling bottleneck in 7970/680 dual card setups:

http://forums.overclockers.co.uk/showthread.php?t=18390360

But in your case it's quite a costly upgrade for a scant few fps more(probably only see a slight improvement in BF3) when it's probably running fine as it is anyway.

Yeah, no way I can afford to splash out of £600 for mobo,chip and ram just for a few more FPS.

680 sli has been a very good jump from 5970!...thats plenty for a long while.

Crackatoah · 15 Apr 2012 at 21:05

If its running at 8x (which even though they say two lanes at 16x most motherboards only run at 8x 8x when two GPU's are installed) then its probably bandwidth bottlenecked, if it is at 16x then not sure

James J · 15 Apr 2012 at 21:24

Do you have the option of "prefer maximum performance" enabled in the nvidia control panel under the power management tab? Also, using adaptive vsync or not?

Rusty0611 · 15 Apr 2012 at 21:30

Crackatoah said:
If its running at 8x (which even though they say two lanes at 16x most motherboards only run at 8x 8x when two GPU's are installed) then its probably bandwidth bottlenecked, if it is at 16x then not sure

I don't think it's being bottlenecked due to 8x

Edit: Why is it whenever I see a BF3 screenshot, I really want to play? You don't fully appreciate in the midst of battle sometimes what a beautiful game it is.

chipachap · 15 Apr 2012 at 21:44

tommybhoy said:
According to this thread, 2600K upwards is needed to remove the scaling bottleneck in 7970/680 dual card setups:

http://forums.overclockers.co.uk/showthread.php?t=18390360

But in your case it's quite a costly upgrade for a scant few fps more(probably only see a slight improvement in BF3) when it's probably running fine as it is anyway.

I started that thread and going from a 2500k to a 2700k made a big difference for me, but it didn't fix it completely. It improved it a lot in 48 player TDM/Rush and smaller maps/games.

But when you play 64 player CQ on say Gulf of Oman or Caspian Border my usage used to go down to ~60% and if I turned down settings usage would drop and no FPS increase. Now in those same areas it stays around ~80& usage and the game really feels a lot smoother. I haven't gotten any lag spikes yet, I got a few here and there with a 2500K.

It shouldn't be a CPU bottleneck because my CPU would only be around 65-70% but the extra threads seemed to help. I don't know if it's a x8 2.0 PCI-E bandwidth issue or if the game is just badly written for big maps mixed with low resolutions, people don't seem to have the issue at 2560X1440 and above.

Soundood · 15 Apr 2012 at 22:00

TallPaul_S said:
Its the first line in the command line in the screenshot he posted, "Render.PerfOverlayVisible 1"

any way to put this in a start up script? like we used in Crysis wars?

Crackatoah · 15 Apr 2012 at 22:11

It does sond like a 8x bandwidth bottleneck.

With two 580's in SLI the 8x bandwidth doesnt bottleneck but it does just about reach its limit, so two 680's which is basically nearly twice the power I think it could well be bottlenecked a bit by 8x

Rusty0611 · 15 Apr 2012 at 22:17

Twice the power?? It's not even close.

bru · 15 Apr 2012 at 22:21

x58 chipset can do SLI 16x it only drops to 8x when using 3 or more cards as far I know.

Remember that the discussion about a 2500k being a bottleneck was mainly revolving around the extra threads the 2600k has, Inoton's i7 920 also has the extra 4 hyper-threaded threads.

Obviously the clock speeds are quite a bit lower with your CPU. Don't forget your only running 6GB of ram, even though i have no idea how this would effect things in BF3.