9800GTX+ Sli Unstable

[bmicd]

I've kinda let this slide for a while. I originally built my PC with a single one of these cards with no problems. A few months later, I decided to grab another one for SLI purposes. Ever since, I haven't had much luck.

It started with strange artifacts, like horizontal lines of orange/pink/whatever. Through searching people have said it could be a bridge issue. I originally couldn't solve it, but somehow through a stretch of time I managed to get the horizontal lines to disappear (definitely not a driver issue). It was then that I noticed SLI with these two cards just was not stable. After maybe a minute of playing, components such as my keyboard would flicker off then back on. Games would crash. Drivers would fail. Sometimes even BSODing would occur. NOTE: this is only while using SLI. I'd really like to know what the issue is.

Specs (relevant to the post):

EVGA 790i Ultra FTW motherboard
(x2) EVGA 9800GTX+ 512mb graphics cards
Intel q9400 2.66ghz Quad-Core CPU
(x2) G-Skill 2gb DDR3 RAM
Thermaltake 750W PSU

 

[Maziar]

Do both cards work stable in single mode ? Don't you get any errors with either of them ?
Also make sure you have the latest VGA drivers installed

 

[megamanx00]

How are the Temps when they are in SLI?

 

[bmicd]

@ Maziar, both cards work fine when used in single mode. I even tested the secondary PCI-E slot by running a single card off of that as well. All checks out. My latest video drivers are also installed.

@ megamanx00, the temperatures rarely go above 62 degrees.

 

[Maziar]

How many bridges are you using ? if you are using 2,then check with 1 and see if it helps.
Also update your motherboard's BIOS to the latest version

 

[nforce4max]

Check for corrosion on the connectors and the cables if you are using non stock cables but check any way. Then do a load test with both cards installed but with out sli being enabled using any game or program that uses physx or gpu based computing to produce load on both gpus (you can select which one for single test).

 

[bmicd]

@ Maziar, I have a single bridge connector and a double-sided bridge connector. I have tried both with the same result. My motherboard was updated to the latest version (P10) about a month ago.

@nforce4max, How can I select which card to test the load on? I'm currently downloading 3dmark06. Is this the correct way to test it?

 

[rsmith13]

Maybe your power supply isn't up to the task of running 2 graphics cards at full throttle.

 

[bmicd]

http://www.newegg.com/Product/Product.aspx?Item=N82E16817153036

There is a link to my PSU for further dissection.

 

[Maziar]

Can you test with another PSU ?

 

[bmicd]

I unfortunately don't have access to any PSUs more powerful than that.

 

[Maziar]

It maybe your PSUs fault that's why i recommended to test with another one, but if you can't,then its difficult to find whether the problem is hardware or software related

 

[bmicd]

I can pretty safely conclude it's not a software issue. I'm leaning more toward the fault of the motherboard. I've had various issues with system freezing or BSoDing when overclocking either my CPU or RAM. What are your thoughts on this?

 

[nforce4max]

It is quite possible but it is going to be difficult to pinpoint unless you have another system or a friend/family/coworker who is willing to let you test your cards in it.

 

[Maziar]

+1^
As for OC'ng,those freezes/BSODs maybe because the OC wasn't stable.

 

[bmicd]

It was a relatively simple OC. From 2.66ghz to 3.0ghz on the CPU.

 

[Maziar]

But it can be unstable.(even the slightest of OC's can cause instabilities)

 

[bmicd]

I'd like to add that even with my previous PSU I had the same issue. It was 700w and SLI-certified. It died several months ago and upgraded to my current one mid-December.

 

[nforce4max]

Well we all have some type of parts that we don't have good luck with but perhaps you look deeper into system and experiment to see ware the issue is. I suggest going back to default clocks and try sli then. If the system clunks up again then you got a hardware issue some ware. Do you got an old hdd that you can load windows on to just to try and rule out software being an issue?

 

[bmicd]

I have reformatted and even installed drivers from scratch before with no success. I have also tried SLIing with default clock settings as well.

 

[nforce4max]

Hardware then, it could be the psu or the board since you have already said that you had tested each card seperatilly.

 

[bmicd]

I'm going to look into the PSU being the answer first. What would be more symptoms of an underpowered PSU? What are ways to tell, mathematically preferred, that my PSU is compatible with everything in my system?

 

[nforce4max]

It is possible that it isn't keeping a stable voltage for your system or the board has a fault. You need to find some one in your local city that is willing to let you test your cards in sli.

 

[bmicd]

Ah, if the potential issue is that the PSU has a fault and not that it just isn't powerful enough then I'm not too confident the PSU is the issue.

 

[nforce4max]

Well there isn't much that can be done testing wise so you may just have to live with your current issue to you are able to rule it out. Either you find another rig to test your cards or buy more parts you wont know the problem but you can sell your cards and get one single card that is on par with your two cards performacne wise but that wont be cheap especially out side the US unless you know ware to sell/shop.