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Problem with SLI effectiveness

Last response: in Graphics & Displays
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June 7, 2009 12:11:30 AM

About a year ago I built a system with a BFG 9800 GTX OCX card and about a week ago I figured it was time to do some upgrading. I checked pretty well every reputable E-tailer I could think of and they don't sell that exact model anymore. I thought nothing of it and bought an EVGA 9800 GTX+ that had just about the same clocks in every department and I overclocked it to bring it up to speed with the first one and put them in SLI but I am getting almost no increase in performance. The two "benchmarks" I've tried are 3DMark06 and Crysis and I got within 200-300 3DMarks and no noticable increase in fps on Crysis. The one thing that I did notice about these two cards is that they use different drivers for some reason. The BFG card uses a driver called 9800 GTX+/ 9800 GTX and the EVGA takes one simply called 9800 GTX+. The cards are still able to go into SLI under the Nvidia control panel but nothing really happens as far as performance. If anyone could help me it would be very appreciated.

Other system specs that could impact this situation:
Q9300 2.5 GHz OC'd to 3 GHz
2 GB G Skill DDR2 RAM 800 MHz
Antec 900 Case
Tuniq Ripper 1000 Watt PSU
Also, these tests were at 1280X1024 with no AA but I have read something about the lower resolutions being not as affected.
Thank you for any help or input


June 7, 2009 12:40:34 AM

your resolution is your problem, you really won't see much of anything different since at that resolution your fps is CPU bound (so those somethings that you read are true)
get a monitor capable of 1920x1200 to really see those shine
June 7, 2009 12:48:42 AM

Quote:
your resolution is your problem, you really won't see much of anything different since at that resolution your fps is CPU bound (so those somethings that you read are true)
get a monitor capable of 1920x1200 to really see those shine


Okay, thanks. That's what I figured the problem was, I just wasn't sure if the slightly different cards that were causing it or what. One more question though, would it increase my performance overall if I increased my res? Like if I got 25 fps on Crysis at 1280X1024 would I get more fps if I went to 1920x1200 or would I just get about the same fps but obviously look better? It doesn't make sense to me that it would but then again I didn't figure that the resolution would make a difference. lol
Again thank you mindless728 and to anyone that has any other input on this question.
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a b Î Nvidia
June 7, 2009 12:50:55 AM

Yeah, you're probably limited by your CPU at that resolution. You would see a big difference on Crysis on a 1680x1050 monitor though. Anyway make sure that SLI is enabled in the NVIDIA video control panel, just to make sure they are indeed running in SLI :) .
a b Î Nvidia
June 7, 2009 12:53:58 AM

Hmm.......... 25fps? Yeah check the control panel on that. Better yet use GPU-Z. Also make sure that the SLI cable is properly connected on both cards.
June 7, 2009 1:00:43 AM

Quote:
Hmm.......... 25fps? Yeah check the control panel on that. Better yet use GPU-Z. Also make sure that the SLI cable is properly connected on both cards.


First of all thank you for the response megaman. And "25 fps?" was exactly what I was thinking. I'm pretty certain that they are connected as they are supposed to be but what would I check in GPU-Z?
a c 171 Î Nvidia
June 7, 2009 1:10:46 AM

requiem217 said:
"25 fps?" was exactly what I was thinking. I'm pretty certain that they are connected as they are supposed to be but what would I check in GPU-Z?

Work that CPU baby! [:mousemonkey:3] , 1680 x 1050 is the minimum that you want to run with those two cards and just to be sure that SLI is enabled, have you enabled the SLI indicators?
June 7, 2009 3:17:09 AM

Mousemonkey said:
Work that CPU baby! [:mousemonkey:3] , 1680 x 1050 is the minimum that you want to run with those two cards and just to be sure that SLI is enabled, have you enabled the SLI indicators?


Alright, then. I guess I'll have to get a decent monitor. Thanks again to all of you that helped a humble SLI n00b.
June 7, 2009 4:33:22 AM

Sometimes a 9800 GTX and 9800 GTX+ don't like to play together, as seen in these two posts.

http://www.evga.com/forums/tm.asp?m=100612750

http://www.evga.com/forums/tm.asp?m=100630844&mpage=1&k...

Sounds like the guy fixed a lot of his problems by putting the GTX+ in the first slot and the regular GTX in the second slot (and doing the same with the SLI bridge.) You may as well try this before spending a bunch of money on a monitor.

Also, SLI in low resolution works perfectly fine...it's just that most cards/games don't really need extra help at low resolutions and you tend to run into CPU bottlenecks quickly. In Crysis, at 1280x960, Turning SLI on and off changes my framerate by some 25 fps! Anandtech did a review that included a Crysis benchmark with gtx 260 sli at 1280x1024. A single gtx 260 scored 45.6 fps, while gtx 260 SLI scored 64.8 fps - that's a significant improvement at a low resolution with a powerful card. You can see from this other review that a pair of gtx 280s also scored about 64.8 fps, meaning the gtx 260s could've scaled even higher, but they hit a CPU bottleneck. Point is, SLI at low resolutions work, it's just usually not feasible/necessary.
June 7, 2009 12:57:22 PM

efeat said:
Sometimes a 9800 GTX and 9800 GTX+ don't like to play together, as seen in these two posts.

http://www.evga.com/forums/tm.asp?m=100612750

http://www.evga.com/forums/tm.asp?m=100630844&mpage=1&k...

Sounds like the guy fixed a lot of his problems by putting the GTX+ in the first slot and the regular GTX in the second slot (and doing the same with the SLI bridge.) You may as well try this before spending a bunch of money on a monitor.

Also, SLI in low resolution works perfectly fine...it's just that most cards/games don't really need extra help at low resolutions and you tend to run into CPU bottlenecks quickly. In Crysis, at 1280x960, Turning SLI on and off changes my framerate by some 25 fps! Anandtech did a review that included a Crysis benchmark with gtx 260 sli at 1280x1024. A single gtx 260 scored 45.6 fps, while gtx 260 SLI scored 64.8 fps - that's a significant improvement at a low resolution with a powerful card. You can see from this other review that a pair of gtx 280s also scored about 64.8 fps, meaning the gtx 260s could've scaled even higher, but they hit a CPU bottleneck. Point is, SLI at low resolutions work, it's just usually not feasible/necessary.


Okay, so my CPU is what is causing the SLI not to be as effective. But it should be pretty adequate with a Q9 series running at 3 GHz, right? And if I do need to overclock it even more, what would be safe and adequate with air cooling?


a c 171 Î Nvidia
June 7, 2009 1:25:21 PM

requiem217 said:
Okay, so my CPU is what is causing the SLI not to be as effective. But it should be pretty adequate with a Q9 series running at 3 GHz, right? And if I do need to overclock it even more, what would be safe and adequate with air cooling?

Your CPU is fine, and yes SLI works below 1680 x 1050 but if you want to see how much work the cards are doing then run the SLI indicators.
June 7, 2009 6:32:33 PM

requiem217 said:
Okay, so my CPU is what is causing the SLI not to be as effective. But it should be pretty adequate with a Q9 series running at 3 GHz, right? And if I do need to overclock it even more, what would be safe and adequate with air cooling?


No, that's not what I meant to say, sorry if my post was confusing. I was just trying to clarify that SLI doesn't magically stop working at low resolutions, it's just usually not practical. A 3 ghz Q9 series is plenty strong enough for practically every single game out there.

Like mousemonkey said, turn on SLI indicators to see if the workload is being balanced correctly. You might have one card just hanging out not doing any work even though it looks like SLI is enabled. If the cards are working correctly, the indicator bar will be mostly full (here's an example of a full SLI indicator.) If the indicator bar is only partially filled, it means your cards are not working very hard at all, and there is a problem (here is an empty sli indicator.) A couple things to note; the sli indicator will probably do weird things while you're in menus and loading screens and movie clips - ignore those results. Also, it's not a bad thing if the indicator is moves around a bit. There will be some moments in games that are very CPU intensive and your cards will relax their work showing an empty sli bar. That doesn't necessarily mean there's a problem. There *is* a problem if your indicator stays almost empty the entire time, though.
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