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GTX 580 SLI Low GPU Utilization

Last response: in Graphics & Displays
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February 15, 2012 12:34:17 PM

Greetings my fellow high end gamers with an insatiable desire to max out every game on your system with little respect to cost. :D  I am amongst you and have run into an issue moving from a single GPU setup to a SLI configuration and am looking for some help.

The Need
I play at 2560x1600 so I am unable to play some of the more recent games at max settings with a single GTX 580 (BF3, Skyrim, Batman AC). So I just splurged on a 2nd GTX 580 with the impression that I'll be able to max these games out and maintain playable frame rates.

The Problem
Once I had the 2nd card and the latest drivers installed I immediately pulled up BF3 to see what kind of performance boost I've received. To my suprise, my fps were virtually the same as with the single card at the same in game settings.

BF3 In-Game Settings
All ultra, v-sync off, motion blur off, no AA, SSAO

Single Card Performance Baseline (BF3)
GPU Temp - 65c
GPU Utilization - 99% (maxed - good)
CPU Utilization - 40-60% (not maxed - good)
FPS - 45-50 fps (very stable)

SLI Performance (BF3, same settings)
GPU Temp - 65c (GPU1), 60c (GPU2)
GPU Utilization - both cards jump around from 45-75% very erratically (no where near maxed - not good)
CPU Utilization - 40-60% (not maxed - good)
FPS - 50 fps average,with some eratic spikes (that probably coincide with the GPU utilization spikes)

My System Specs
i7 920 @ 3.2GHz
6 gig RAM, 1333MHz
GTX 580 1.5GB x 2
Mobo: Gigabyte EX58-UD4P
1000W PSU

Questions

1. Does anyone else play BF3 at 2560x1600 with GTX 580 1.5GB cards in SLI? If so, could you provide the type of fps you get and at what settings? Also any info on your system would be appreciated.

2. Is it possible that I did something wrong in setup that would cause low gpu utilization?

3. My first thought with low utilization is that my cpu must be bottlenecking. Highest it spikes is 75%, and seems to average around 60%, so that's not the case. Is it possible that the vram is bottlenecking? Is there any way I can check vram utilization? Can't seem to find an option for that in MSI Afterburner.

4. Could a faulty SLI bridge cause this? What kind of symptoms would you observe if you had a bad one? I am using an old SLI bridge that was laying loose in a box in my basement for over 2 years so I can't be certain of the condition. I don't have a 2nd sli bridge to test. When I get home tonight, I could remove the SLI bridge and see if I can observe any change in performance to determine if it is fully functional. If my system performs the same, I could reasonably conclude I may need a new bridge.

5. Any other ideas or thoughts? Kind of frustrating to spend so much money and observe virtually no gain in performance.

Thanks in advance for any ideas / suggestions!
a b U Graphics card
February 15, 2012 12:42:19 PM

So...What motherboard do you have? What are your COMPLETE system specs?
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a c 88 U Graphics card
February 15, 2012 12:46:57 PM

Hey there, at your huge res I'd suggest you drop more system ram into your rig as games like BF3 utilise alot of memory especially at your res and at Ultra/Max settings.
I currently game at 1920, and I watch my system ram usage being at approximately 5.5gb at times. With your high res you may be topping out with the 6GB. Alt control Delete during gameplay and have a look if your system ram usage is topping out , if it appears to be , adding a couple more gig may elleviate your problem with BF3. When I had 4GB my 560ti SLI set up was struggling in BF3 due to this , so I added another 4GB to take it up to 8GB and now the game plays really well.
Its a good idea like you said to try another SLI bridge , you can get one cheap off ebay. Worth a try just in case but it might not be that at all.
Go into settings and Monitoring in MSI afterburner , there will be a check list where you can select the vram to be monitored.
Best to do a clean install of your graphics drivers and download the latest driver from Nvidia.
Another thing to check is your settings in the Nvidia control panel , make sure your settings are set to run at maximum performance for your SLI. You can also add a BF3 profile in the settings.
Overclocking your cpu may also give you some more juice to your set up.
Sorry about the long read , worth trying everything to get your system running right.
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a b U Graphics card
February 15, 2012 1:22:33 PM

overclock your cpu higher and see if that will increase your fps
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February 15, 2012 6:03:40 PM

Thanks for the responses guys. I'm still compiling data so I'm just adding an update as I went home for lunch to do more testing.


More info -

- My system RAM utilization when I play BF3 is at 4.7 out of 6.0 gig, or 78%. That's getting up there, but I don't think this is creating a bottleneck.

- My vram use is at 1433MB out of 1500MB on both cards when playing BF3. Seems like I may have a vram bottleneck. I guess this may explain the poor gpu utilization with BF3, but I tested a couple of other games and ran into the same thing without the high vram use, so this isn't the root cause of the issue (see next bullets).

- Tested Skyrim. GPU utilization was all over the place, but averaging 60% per card. FPS was around 70. That's fine, but that is the same fps I get with 1 GPU that operates at 99%. VRAM was not an issue here as 950 out of 1500MBs are being used.

- Tested Saints Row the Third. Same story. GPU utilization varied greatly, but probably averaged about 60%. FPS were around 45 with vram use around 900MB. Again, I can get 45 fps at the same settings with a single card since that operates at 99% gpu utilization.


Still have other things on the list to try when I get home from work tonight.

1. Experiment with the SLI bridge to make sure it is functioning correctly.
2. Clean install of the drivers.
3. Test against some more games with documented benchmark performance on GTX 580s in SLI, such as Just Cause 2, Metro 2033, and Crysis. I'll compare my results and if I don't see the same thing, something else is clearly wrong. Seems on average, I should expect 63% increase in fps (up to 95% depending on the game). http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_5...
4. May swap cards around to make sure I don't have anything wrong with the mobo and make sure my new card is functioning correctly (I'm using my older one as the primary).
5. If none of that works, get my sledge hammer out and make some really expensive scrap. ;) 

Clarkjd - I'll post my complete specs tonight. I created this post at work so I am going off the top of my head right now.
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a c 88 U Graphics card
February 15, 2012 6:06:32 PM

Definately start with the clean driver install :) 
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February 15, 2012 6:13:41 PM

monsta said:
Definately start with the clean driver install :) 


Will do. Would hate for that to be the issue if I go through all of that other work first!
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February 15, 2012 6:18:54 PM

Have you enabled SLI in your Nvidia Control Panel?
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February 15, 2012 7:13:14 PM

clarkjd said:
So...What motherboard do you have? What are your COMPLETE system specs?


I second this^

Knowing your mobo might help in troubleshooting.
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February 15, 2012 9:48:51 PM

loganvito said:
Have you enabled SLI in your Nvidia Control Panel?


What this guy said ^

Go through that panel and make dead sure it's enabled.
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February 16, 2012 1:10:16 AM

AidanJC said:
What this guy said ^

Go through that panel and make dead sure it's enabled.


Yes, it's enabled. I've been turning it on and off to compare benchmarks.
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February 16, 2012 1:11:47 AM

bacole08 said:
I second this^

Knowing your mobo might help in troubleshooting.


My mobo is a Gigabyte EX58-UD4P.
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a b U Graphics card
February 16, 2012 1:49:41 AM

heids24 said:
My mobo is a Gigabyte EX58-UD4P.

Which 2 slots are your vid cards in?
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February 16, 2012 2:11:41 AM

Alright, update #2
Did a clean install - may have made a small impact. Had some artifacting going on prior and this seemed to have cleared most of it up. Didn't notice too much in terms for performance gains though.

Collected some more data around other games. Very mixed and erratic results. Crysis 2 and Metro 2033 had some nice gains (57% and 75% respectively) Both gpu's were utilized much better than in other games, at around90%. Saints Row 3, Skyrim, BF3, and Batman AC saw minimal increases (23%, 16%, 34%, and 5% respectively) and had very poor gpu utilization when in SLI. Also had quite a bit of variabilty compared to a single fully utilzed gpu.


Those numbers just don't seem right. Are my expectations too high in thinking that I'd see at minimum 50% improvement in virtually any current game? Everything I've read about GTX580 SLI is that it scales quite often at 90% at the resolution of 2560x1600. I'm just not seeing that. I guess I'll keep digging.
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February 16, 2012 2:13:57 AM

clarkjd said:
Which 2 slots are your vid cards in?


PCIEX16_1 and PCIEX16_2 - my primary card being my older card.
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a c 88 U Graphics card
February 16, 2012 5:34:51 AM

what psu are you running?
Are the 580's running off seprate lines from each other from the psu?
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February 17, 2012 6:11:20 PM

Update #3 - For those following along.

I think I figured out what was at the crux of my low gpu utilization and lower than expected SLI performance.

I tried numerous things since my last update, to no avail. I reseated the SLI bridge, moved the bridge to the other set of connection points, swapped the card position, etc.

Finally I was going to attempt to increase my overclock to see if that made any difference. Went into my BIOS and low and behold, my previous overclock at 3.3GHz had been overridden and was reset back to default due to some start up error at some point in time (according to an error message when I went into the BIOS). DOH!!! Basically, I was running my i7 920 at stock frequency of 2.66GHz while thinking I was at 3.2GHz.

So I overclocked in stages, 3.3GHz, then 3.8GHz, then settled in at 4.0GHz. At each stage I took performance measurements of a few games. I found that at each new overclock level, my gpu utilization increased a bit and I got more fps. At 4.0GHz, my gpu utilization on Saints Row 3 is jumping around between 70-90%, up from 50-75%. Still not fully utilized, but considerably improved.

Interestingly, it seems that my cpu is still somewhat of a bottleneck at 4.0GHz as the gpu's are only 70%-80% utilized in several games (BF3, Saints Row 3, and Batman Arkham City). Other games such as Skyrim and Crysis 2 are 99% utilized though - so I'm assuming these games are less cpu intensive and therefore are able to peak the SLI performance.

Anyway, I'm pretty satisfied with what I'm seeing now. At least I understand why and have been able to make some nice gains by resetting my overclock. Thanks to all for offering your assistance.
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February 21, 2012 5:50:35 PM

Glad you found the problem and was able to resolve. I'm glad you figured out the problem because I plan to build a 580 SLI system in the near future and will be sure to OC my i5-2500k as much as possible to get the most out of it. Thanks.
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a c 595 U Graphics card
February 21, 2012 6:22:11 PM

Be sure to crank up the graphic settings. Your VRAM usage for Skyrim is well below mine. Be sure to use the new official HD texture pack and try to turn on Transparency Antialising to at least 2x Supersampling, even try 8x. Set Ambient Occlusion to Quality and Texture Filtering Quality to High Quality. That should push your GPU's a little harder.

Be sure to try out the new WHQL 295.73 drivers that just came out today.
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