Worse performance in SLI 9800gt

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Hey Guys,

I come to you in a last ditch attempt to troubleshoot a problem I'm having with my two 9800gt in SLI.

It seems I'm getting a 40-50% decrease in benchmark/game performance when I'm running these two cards in SLI compared to a single card. It's quite confusing as both of these cards run an OCCT benchmark at around 170FPS independently but when I enable SLI in the Nvidia control panel the performance drops to around 90FPS. Which indicates that each card by itself is fully functioning and the problem lies with the SLI

At first I thought this may be a power issue as both cards were OC'd along with my CPU and may be drawing more power than my not-so-great PSU can output but this problem persists at stock/underclocked speeds. I've read mixed power requirements for these cards from numerous websites. I'm under the impression at least that they require about 35W-116W each according to: http://archive.atomicmpc.com.au/forums.asp?s=2&c=7&t=9354 give or take a few.

My specs are;
Mobo - MSI K9N SLI Plat
CPU - AMD Athlon 64 X2 5000+ @ 3.1
GPU - Both EVGA 9800GT 512MB (Slightly different BIOS and PCB but I read this wouldn't be a problem)
RAM - DDR2 800 4GB
PSU - Jeantech JN120F-600AP12V2 (3.3@32A, 5@60A(330w Combined), 12.1@19A, 12.2@19A(440w Combined) 575w max 2xPCI-E oulets
OS - MS Windows 7 Ultimate 64-bit 7600/Ubuntu 11.10
Nvidia Driver - Latest 285.62
ForceWare version: 285.62
(Yes, I need a major upgrade, I know)

So my question is Do I need a new PSU? A new card? Or anything you feel is incompatible with my current setup? Would there be a bottleneck that would cause this specifically(PCI-E lanes maybe?)

I'm inclined to think it's the PSU as both cards work fine independently even OC'd! I thought that maybe 19A on the rail was a little low for SLI although I did swap out my pci-e power cable for one of those 2x4-pin molex to PCI adapters but it posted the same result - Fine by itself, crap in SLI.

Any insight or suggestion would be greatly appreciated as I'm totally stumped when it comes to this. TIA
 
I would certainly consider a new PSU. Jeantech isn't really a respected brand, look for something around 700-800W by Corsair, OCZ or another respected brand. Spend a bit of money on the PSU it will last you, so you will get your moneys worth
I am still running a 620W Corsair HX bought around 4 years ago when they were first released that has seen me through a Core2 Duo, Core2Quad, i5, 3 different graphics cards and my now 4890 crossfire solution which is a heavy power draw

I think it may also solve your SLI problem, but I would expect crashes rather than scaling of FPS if power was an issue? But willing to be corrected on that.

Impster
 
A weak or dying PSU can cause,

bad 3D performance
crashing games
spontaneous reset or imminent shutdown of the PC
freezing during gameplay
PSU overload can cause it to break down

Also PSU deteriorate over time, plus Jeantech isnt a good make such as the tried and trusted,

Corsair
OCZ
Antec
Bequiet
etc.

A cheap PSU never puts out the power it claims it does.

One more thing is have you got the latest Nvidia+Motherboard chipset drivers for your OS?
 
@ Impster,

I could not agree with you more of a good PSU being high priority, but I just haven't got the much money to upgrade at the moment as Christmas is just round the corner. After Christmas I will most probably be getting a new build as the am2 isn't really cutting it at the moment.

I was just trying to troubleshoot this problem to get at least, a few more months of gaming out of this computer before I lay it to bed. even if it is the PSU I would like to get some idea of this problem as it's eating away at my insides. It's more of a fact finding mission rather than upgrade solutions at the moment. Thanks for your input never-the-less.
 
@ Stulid

The PSU itself doesn't seem to be having the typical problems associated with a bad PSU apart from bad SLI performance which is initially throwing me off.

The power usage is most probably not giving out it's full potential after the 3 years that I've had it as you've suggested, but after being able to run individual cards OC'd perfectly well using pci-E & running on the molex rail surely it would have enough to power both simultaneously? No?

It's all pretty confusing for me, It seems from even conservative estimates taking into consideration deterioration, it 'should' have enough power. But some of the symptoms indicate otherwise. Maybe it's just my calculations that are off? I'm not an expert on wattage and amps when it comes to PSU's or electrical items in general.

Edit: Also, my drivers are all up to date.
 
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well theres your problem

cheap PSUs can almost never output their rated wattage. occasionally they can in unrealistic tests, but not usually

I agree, but I was doubtful that it would be classed as a 600w but not producing more than 400w that was needed. Seemed a little on the extreme side.
So I'm on a mission so sort this out over the weekend, I'll give you a quick update on what's happening.

Thinking it was the PSU I was sitting here trying to work out why the PSU was faulty considering it seemed pretty rock solid from my personal experience and every test I set the PSU it seemed to pass, I was looking at typical deterioration of PSU's and swatting up on calculating amps and wattage when I realised I had an old PSU that had a faulty fan on it. So I went to dig it out in hope of it being capable on running my rig. Pulled the chrome ricer PSU out and, yes you guessed it, Another Jeantech!(Don't hate me) I remember getting this one solely because it was the only one left in PC World.

The problem was it was a 450W JN120F-450-AP with only one PCI-E Powerplug. But I gave it a shot anyway, hooked one 9800gt up to the PCI-E plug and used a 2-molex to pci-e6 cable to power the 2nd one. Low and behold, it booted up! Who would have thought that?

So now to the moment of truth, opened up OCCT impatiently waited 60 seconds for it to actually run... And ....Exactly the same problem =( - SLI enabled, Score 94FPS. SLI Disabled, score: 167. WTF?

So I'm thinking drivers... It must be the drivers, went to MSI downloaded the recommended MOBO drivers using live update(Which were different from Nvidias newest drivers) - Nothing, same result

Video drivers - Seeing as I had the latest installed I decided to try older versions that were confirmed for working 9800gt SLI configs: 257.21, 275.27 & 280.26 - No Luck

The OS - This was kinda a long shot but maybe it was some sort of driver conflict so I decided to switch to Ubuntu 11.10 and try this out, apart from it taking me forever to source a good benchmarking (unigine_heaven-2.5) I was ready to give it a bash. Tried it with multiple resolutions and tessellations and it was almost the exact same across the board. I'm not sure if this is a configuration problem or the fact the SLI in Linux is notoriously crap. But more importantly there's no better performance to be had. I would have seen this as an improvement from the 40-50% worse performance I was getting but I do have a few games where sli & non-sli yield the same results, so, still not any closer to finding what the problem is. My thoughts are shifting towards the MOBO at this time, but there's little I can do to test that if anything.

So at the moment I'm trying to dig a little deeper into the config files to make sure it's set up correctly, I'll post back with sporadic updates when I have them.

Update 1: Seems the I needed to restart in order for the xconf file to be updated, ran the unigine benchmarks again and It's worse performance in SLI than a single card *Sigh*



So last ditch effort, gonna flash the mobo bios to an older version in the hope that it may alter how the northbrige works. Doubtful tho. Other than that it has to be the mobo that is the issue.

@Cupra
Thanks for the suggestion, I never really thought about that, I'll look into it and report back. I've tested it with and without the sli bridge on, same results.

Update 2:

So I tried the paperclip trick with the other PSU, same problem. So that pretty much isolates the problem to the motherboard?
PSU - fine
Cards - fine
I can't think of anything else that would cause this problem? For OCCT benchmark the CPU/RAM aren't really included so I seriously doubt it's a problem with them.

With regards to the PCI-E slots k9n-sli plat has dual x16, Initially I thought this may be an issue as well as the performance is almost halved when in sli.. Maybe the bandwidth of the top slot could be limited and SLI is causing twice the data throughput? But I'm not sure if that's how SLI works though, it could still be an issue with the PCI-E slots, Wouldn't know how to identify that tho or what the symptoms would be, I've never heard of a slot acting like this =/ Thanks for helping rule out the PSU though!

Update 3:
So updated the BIOS, or should I say downgraded to an older version, no real change in benchmarking performance thought which has kinda left me at a dead-end.
One nice thing though is after downgrading vga drivers to 197 BF3 instead of slowing from 40fps to 3fps in sli has now returned to playing at 40FPS with or without SLI, I presume that would've just been the latest driver being ****. But to be honest that has just made it so I can play BF3 in SLI at the same framerate and detail as Not in SLI, pointless.

Nothing else to try, motherboard being the main culprit. I've ticketed MSI customer services to see what they have to say about it, I'll let you know what they say, also requested beta bios for my mobo as it seems to support my CPU better.

Thanks for the suggestions.
 
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why not try both psu's at the same time just jumper one off using a paperclip from the green to any black ont he 24pin part of the psu, use the lesser powered psu to power 1 gpu the other to power everything else, if they both run 1 card and the pc fine this should eliminate it being the psu

it could be somthing as simple as a dodgy sli bridge

its also worth mentioning that the mobo you have only runs @ 8x in sli so it could be hurting performance a little (your cards are pci-e 2.0 and yout board is 1.0 meaning its getting 8x+4x in modern standards)

also try upping the pci-e frequency to 101 that can help
 
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I think I've figured it out I'm not 100% sure though, looking through NiBitor 6.03 i was scanning through all the windows and came across this;

Seems the one I have just purchased it actually a flashed 8800GT. I'm not sure how this would effect sli performance as a quick route around google seems to suggest that they would work in SLI fine, even at different fabrication processes. This may be a side effect of different PCB?
 
From memory I think the 9800GT and the 8800GT are exactly the same only the 9800 is a smaller chip size like you said.
 
@Nickyyy

Yep, been looking around at people who seemed to have flashed their 8800GT with mixed success, Most of them who failed got a dead card, some it wont enable sli & for the rest that worked, they were all able to enable SLI which seems to be a sign of it working... Mines is enabled no probelm & seems to work perfectly in sli too apart from this issue which I don't think is related. the PCB boards don't even have to be the same to flash it which is quite surprising. Even EVGA themselves flashed a bunch of 8800GT's, rebranded them and sold them. One of which I think I have, it has an EVGA 9800GT case graphics on it anyway =/

So no closer to figuring it out.
 
wait... so we tell you that the problem is almost certainly that you have a rubbish brand of PSU and that its underpowered, so you try a LOWER rated PSU from the SAME brand. i wonder why i post in these threads sometimes.

please let me persuade you to get a new PSU even if you think it isnt the problem:

jonnyguru: death of a gutless wonder
jonnyguru: death of a gutless wonder II


they may not be reviewing jeantech's, but i would rate those brands similarly to the jeantech
 
@Reaper

I don't think you quite understand. Rubbish or not, it has been rock solid for me and has shown no problems what-so-ever to indicate that it's under-powered. I can run 1 OC'd 9800gt(at full fps) another 9800gt not in sli but plugged in, OC 5000+BE, 4 drives, 3 fans, 4 dimms. no problem at all. Not even a whiff of it struggling. I can run any game, any length of time while not-using sli.

Okay, now, I take out 3 drives, 1 fan, stock everything & enable SLI
-In games exactly the same, no performance gain
-In benchmark 40-50% lower

The voltages are spot on. checked them in bios and in windows while under stress.

I understand that good amps on the rail is needed and I have enough, I'll reiterate my reasoning in ruling out the PSU.

When not in SLI my computer runs perfectly, OC'd or not, loads of drives/hardware connected or just 1. Seemless. When I put it into SLI with limited hardware connected i get 40-50% performance.

So If I can run 1 9800GT with multiple OC's then The wattage on that rail is sufficiant. Otherwise, it was show problems.

I can also run the same single 9800GT from a 2xmolex to 6-pin PCI adapter(Note: My psu has 2x6-pin pci-e adapters, I was just trying to keep the load on that rail to a minimum to isolate any lack of power on the 12v line) at full load OC'd

So I have enough power to run a single 9800GT at full load and OC'd on both the 3.3v/5v and on the 12v rail. But when they have SLI enabled I get 40-50% worse benchmarking performance. My games still run at the same speed as 1x9800gt but no improvement in games and worse when benchmarking.

So, maybe the 3.3v/5v hasn't got enough power? Well this is where I pull out my old 450W psu and do the paperclip trick and use the dedicated rail just to power 1 GPU and use my 600W to power the other(I also tryed to power both gpu's with the 450w to reduce load on my 600w). So am I right in thinking that this will be enough power? After all, the PCI-E power pin as far as I know can only output a maximum of 75 W!! Meaning the 250w extra i have on the rail in the 450w is extreme overkill. and being that I know that my 600w can power one by itself the 600w can't be a problem, can it? Even when every time I try in sli it's always stock clock speeds(GPU&CPU)

So I don't know about you, but I think that's pretty conclusive? Or maybe I'm reading this totally wrong, I would love for someone to correct me on this.#

Edit: Haha, I like the vid. 'Spectacular!'
Anyway, I thought you should recalculate your opinions, Jeantech are not THAT bad, http://www.tomshardware.co.uk/stress-test,review-1362-20.html This is a slightly different PSU but has the same model number & is identical apart from an extra 6 pin pci-e connector and 10 more watts on the 12v rail.
It's average, not a cheapy PSU that costs £20.
 
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when you are doing the two card test not in SLI are you maxing out both of them, or just the one? if its just the one then i'll stand by poor PSU verdict, but if its both then its looking like the problem lies elsewhere

also, im very surprised at how well that jeantech is doing. its still not very good, but its no where near as bad as i thought it would be
 
when you are doing the two card test not in SLI are you maxing out both of them, or just the one? if its just the one then i'll stand by poor PSU verdict, but if its both then its looking like the problem lies elsewhere

also, im very surprised at how well that jeantech is doing. its still not very good, but its no where near as bad as i thought it would be

It doesn't max out either but it utilizes about 50% of GPU core on each card when i bench with SLI. so both cards are working at 50%

I'm going to buy a multimeter offa ebay and test this out, Pretty certain it's not the psu..But I'll find out in a week. Motherboards reading are showing vcore 12v and 3.3v within 3% when under stress conditions which is pretty good. But they're from software monitors that aren't 100% reliable tbh. Would it see a major dip if it was under powered? according to http://extreme.outervision.com/psucalculatorlite.jsp the bare minimum psu I needed for 9800gt sli was 401w, which was surprisingly low. 470ish recommended if my memory serves me well.

Less that I initially thought.
 
You know what I'd do tbh? Find someone who lives near you that has a huge balls PSU and get them to plug it into your rig for you just to test. So much easier :).
 
So, I thought I should wrap this up with a a conclusion if anyone else comes across the same problem.

So against my better judgement & after I eBay'd some random junk off, I gathered up some dosh and bought a Corsair TX650. With my fingers crossed I whacked it in, booted up & ran OCCT GPU benchmark.

Unfortunately the problem persists. So seeing as both GPU's run flawlessly individually, I think it's down to a faulty motherboard. I've got a multimeter due in the post soon to triple check the PSU, but I doubt that will show otherwise.

If anyone is knowledgeable about troubleshooting motherboard problems I'm still open to suggestions for isolating the problem further. With my own experience and knowledge I've failed to come up with a feasible conclusion to match the symptoms. All the caps look in order and I doubt the if the southbridge was failing it would cause this problem. But I could be wrong, this is as far as my knowledge will take me.

Thanks for the suggestions anyway.
 
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