Lights are on but no one is home: SLI performance problem!

[Citizen_Z]

I'm troubleshooting my SLI rig and am confounded. I just ran a Fraps benchmark on Need For Speed: Most Wanted with SLI enabled and disabled and discovered the average frame rates for both was IDENTICAL! What gives?!

SLI is properly enabled in the drivers and by virtue of the drivers recognizing SLI I must have the mobo jumpers properly set and bridge firmly in place. I'm using 84.21 drivers. I'm at my wits end. Can anybody help? My rig specs are in my signature block.

edit: I also ran a benchmark with Aquamark3 and discovered that enabling SLI results in only 2000 more points. I don't get why the second card isn't pulling its weight.

edit: wtf! 3D Mark 2006 results in a DROP in performance with SLI enabled. 800 point drop from 5500ish to 4800ish.


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Windows XP Pro
DFI Lanparty SLI-D
Athlon64 4400+ @ 2.4ghz
4x512mb Corsair XMS Pro
2x7800GT @ 490/1150
Maxtor 300/16 SATAII
WD 250/8 SATAII
JustPC 500w (480, really)

 

[Heyyou27]

AquaMark3 won't doesn't benefit from SLI, but there is obviously something wrong with your setup. Your powersupply is only 480W, and you’re using two overclocked 7800GTs with an overclocked CPU.

 

[Citizen_Z]

I thought the normal response to underpowering a GPU was either a crash or an error of some sort. My system is entirely stable.

 

[MrCommunistGen]

You might try reinstalling the drivers. A friend of mine had a similar problem (SLI not helping at all) and after we reinstalled the drivers it worked fine. By reinstalling I mean: uninstall the current drivers first, and then after rebooting install the latest drivers (again?).

-mcg

 

[Citizen_Z]

I've tried reinstalling. In fact, I booted into safe mode, ran Drive Cleaner Pro, rebooted, then installed new drivers to the same effect. I was thinking it was a mobo issue but I have the very newest bios, actually an aftermarket enthusiast bios from... some site I can't remember. I've also tried running it without any hhds or ATAPI devices powered to the same effect so I don't think its a power issue.

I've run both of them in the primary PCIE slot discretely so both cards are good as well.

 

[Ningenpo]

What settings are you using with 3dmark06?

I got a X2 4800 @stock, Asus A8N32-SLI, two e-vga 7800 GT @ stock 470Mhz, 2 Gig ram and normal harddrives not in Raid. 500W PSU

And I get the score ~ 8100p in 3Dmark06 @ 1280*1024 with SLI enabled.

Are you using like 2560*1920 resolution or something?
Sounds weird that you get lower score in 3Dmark06 when you enable SLI...

Try benching each of the 7800s separately only having one card attached to the mb. Try benching everything with stock speeds. Sounds strange, but some of my projects have benched lower beeing overclocked. Borrow a empty harddrive and try with a clean XP install. Try memtest86+...

Good luck!

 

[Citizen_Z]

The thing is, I did some research and most other power supplies that are dual 12v rail are also 20a. This PS has plenty of power on the 12v rails (20amps each). Even some monster 650w ps's are only 20a on each of the 12v rails with some crazy amount, like 56a on the 5v rail to make up the difference. I'm pretty sure it's not a power supply issue. I'm especially reluctant since I'm living in Germany and buying from Newegg takes 2+ weeks and buying locally means 50% higher prices. I guess either way I'm screwed.

This may boil back down to the debate whether having independant 12v rails is better than having a single 12volt rail.

 

[Citizen_Z]

What settings are you using with 3dmark06?

I got a X2 4800 @stock, Asus A8N32-SLI, two e-vga 7800 GT @ stock 470Mhz, 2 Gig ram and normal harddrives not in Raid. 500W PSU

And I get the score ~ 8100p in 3Dmark06 @ 1280*1024 with SLI enabled.

Are you using like 2560*1920 resolution or something?
Sounds weird that you get lower score in 3Dmark06 when you enable SLI...

Try benching each of the 7800s separately only having one card attached to the mb. Try benching everything with stock speeds. Sounds strange, but some of my projects have benched lower beeing overclocked. Borrow a empty harddrive and try with a clean XP install. Try memtest86+...

Good luck!

I've benched each card separatly and they perform right in the expected window with 3DMark05, about 7000pts. Its with normal settings in 3D Mark. I have the free version so I can't fiddle with any settings anyway.

Each card independantly pulled in 6992 and 7004 in 3DMark2005, normal variation and in SLI mode they did 7099, still within two standard deviations from the mean as far as scores on rigs like mine go. This is with stock default settings, 400/1000. I don't understand why that one run came in lower. There may have been something going on in the background I didn't disable.

Basically what it looks like is the second card isn't getting work to do or isn't able to do the work it's given, even though it's properly configured.

 

[Ningenpo]

Ok, that just sound strange with the scores you get. Haven't tried with a single card, but with SLI enabled I get 12900p in 3Dmark05. 3Dmark is very good at using SLI (That's my oppinion anyway). So as you're having almost the same equipment as me you should get about the same score. Some samples are a bit better than other, but there should not be more than +/- 500p deviation.

Can you determine if you have a good balance between the two cards?

I have GTA san andreas, and if I don't disable SLI when playing I get a slightly discolored line splitting the screen in two. When I saw this I took it as evidence that the cards actually divided work. Try enabling "show gpu load balancing", it's in the same screen as where you enable SLI. The green line should be fairly centered if SLI is working properly.

If you still can't get it to work, do as I planned to do for a while. Sell your 7800s and buy the best available 7900 GTX. The two solutions are about on par after what I've read.

PS. Have you updated all drivers and bioses?

I have a 500W Antec Neo2 that's SLI certified from Nvidia. If you can (I done this myself a couple of times in the past) go to a local computershop and say that you're interested in buying a new PSU but that you've had bad experiences therefore you want to try before buying. If you're lucky they'll let you hook your computer (that you have with you) up with another PSU. If it works, run home and order from the net.

Good luck!

 

[Citizen_Z]

Can you determine if you have a good balance between the two cards?

I have GTA san andreas, and if I don't disable SLI when playing I get a slightly discolored line splitting the screen in two. When I saw this I took it as evidence that the cards actually divided work. Try enabling "show gpu load balancing", it's in the same screen as where you enable SLI. The green line should be fairly centered if SLI is working properly.

Hmm... very interesting result. Using split frame rendering, the line is centered in the screen when you first fire up NFS:MW. As you play though, the line gradually moved down to the bottom where it sits regardless the scene or frame rate. Thats definatly wrong. Its like the second GPU is being throttled back as gameplay goes on. I monitored the temperatures and its definatly being cooled properly.

It may actually be a voltage issue but its hard to pinpoint since it does the same thing regardless whether I strip out all unecessary components or not. Additionally, the eXtreme Voltage Calculator linked from the CPU's and Power Supplies section calculates a MAXIMUM of 411w, which is still in the window for my power supply. The heat coming out the back of the PS isn't terribly hot either. Actually its kinda lukewarm so the power supply isn't being taxed.

Oh and yes, all my drivers and bioses are very new; the most recent across the board.

I don't know if this is telling, but after opening up Display Properties and clicking on the advanced tab, it takes fully 15 seconds for the GeForce 7800 GT tab to initialize upon being clicked. Furthermore, it takes nearly 20 seconds for the Performance & Quality Settings option to display upon selection. Is this kind of delay normal?

 

[Citizen_Z]

Ok, I think I've got it. My understanding of how the SLI profiles worked was in error. I had to go in and edit the active SLI profiles but I just pulled in 11625 3Dmarks05 with 400/1000 so I think we're good to go. Thanks for the help guys, but somebody needs to write a no-shit, Barney-style breakdown about exactly how SLI profiles work. They're pretty confusing.

 

[VelvetHammer]

Speaking of 'Barney-style' breakdown. Could you explain what you did when you edited the active SLI profiles, to get the results you achieved?

Thanks...

 

[Citizen_Z]

I didn't really understand how the SLI profiles worked. When I first setup my system I set up an SLI active profile and put all the games on my PC into it. The problem was, I ultimatly had multiple profiles for the same application and it was causing conflicts and the games were running in single GPU mode. I still haven't hunted down all the conflicts but suffice it to say uninstalling the driver didn't remove all the SLI profiles. I actually had to activate the preinstalled profile by selecting it and activating SLI mode in it. User created ones must not be stored in the same location as the default ones because the ones I created were still there after an uninstall/reinstall.