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SLI woes. Please give me some pointers....

Michaeljcox24

Michaeljcox24

Michaeljcox24

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Does this sound right or not, because it's the first time I've been messing around with SLI and its performing worse than than I ever imagined.

1st card: Gigabyte GTX 580 Superoverclock
2nd Card Gigabyte GTX 580 OC

Both @ 800 / 1600 / 2200 in MSI Afterburner, 1.038 V

CPU = 2500K @ 4.6 Board = P8Z68 Pro Gen 3

When I run the concrete jungle bench maxed out in Just Cause 2 on one card with SLI disabled, average FPS is 39, with SLI enabled its 35.

So SLI performs worse than a single card. I don't understand. Is it because I haven't got exactly the same cards in each slot?
 
Michaeljcox24 said:
Does this sound right or not, because it's the first time I've been messing around with SLI and its performing worse than than I ever imagined.

1st card: Gigabyte GTX 580 Superoverclock
2nd Card Gigabyte GTX 580 OC

Both @ 800 / 1600 / 2200 in MSI Afterburner, 1.038 V

CPU = 2500K @ 4.6 Board = P8Z68 Pro Gen 3

When I run the concrete jungle bench maxed out in Just Cause 2 on one card with SLI disabled, average FPS is 39, with SLI enabled its 35.

So SLI performs worse than a single card. I don't understand. Is it because I haven't got exactly the same cards in each slot?
Click to expand...

Something is amiss I get way over 60 using 480gtx sli. Try running it with cuda water simulation off, you may find that it is reserving a gpu for the cuda (wild guess I know).
 
MeatLoaf said:
So power isnt an issue :)

Have you tried the cards at stock?
Click to expand...

This is a sticking point....

Stock clock for the Superoverclock card is 855, where stock clock for the normal OC card is 795. I think the stock voltage for the cards is different too, I know the Superoverclock card stock Vcore is 1.075 but in Afterburner, there is only one slider for voltage, and one slider for core speed (and memory) so I have no way of finding out what the other one needs or wants.

So I set voltage to what seems to be stock for the lightning cards, 1.038 (a little over 1.025)

I assumed the superoverclock card needed the higher voltage to be stable @ 855, but when I run it at this it goes up into the high 80's on Heaven and Tropics benches when SLI'd with the other one.
 
I just increased core voltage to 1.075 and ran a heaven bench. Min FPS was 21, max was 60, but on the 2nd run it crashed halfway through back to desktop. Annoying. I got higher scores and framerates than this on a single 470
 
Flash both cards with same bios might help but save old ones just in case

For some reason your system looks like its using only one card only
 
I've made some inroads since my last post.

I uninstalled Afterburner, uninstalled nvidia drivers, and did a safe mode driver clean. I then re-booted, re installed drivers, rebooted again, and ran a heaven run. Min fps was 62, max was 200 odd.

So yeah, I thought it was a dodgy driver install, so I re-installed afterburner. Did another heaven run, and min fps was back to 20 and max was back to 60.

Did it all again, without installing afterburner, and fps has stayed good on heaven. I have no idea why, but there is something afterburner does, with my two cards, thats forces them to underperform massively.

Thats not the last of it though. Even though fps was good, heaven still crashed about 3/4 of the way in, I had to drop clocks down in nvidia performance monitor right back to stock settings to get stable. Have a feeling the two different clock speeds on the cards are confusing afterburner and causing it to set them wrong.

So yeah, I have good fps now, but no way of changing voltage or monitoring temps. And they wonder why people stray away from sli?!
 
MSI afterburner might be screwing with the clocks, It did that with my 5850.. Although AB said it was clocked at 900MHz it was performing really bad.

Upon testing it had actually set my card to 400Mhz :(
 
there's only one slider for everything, even though your on sli, which makes no sense. if anyone can show me some software now that lets me monitor voltages and temps it would be much appreciated.
 
almighty151986 said:
MSI afterburner might be screwing with the clocks, It did that with my 5850.. Although AB said it was clocked at 900MHz it was performing really bad.

Upon testing it had actually set my card to 400Mhz :(
Click to expand...

I had problems with Afterburner with me non-identical 5850s too.
There is a setting that allows you to use same settings for both cards. Make sure this is NOT checked.

Then you can set which card is Master, under General tab: Master graphics processor selection", go back to main page, check clocks & voltage, etc, save it, then switch the other card to Master and repeat.

It's a bit fiddly and I was never happy with the way it worked. I resolved never to use mismatched cards with AB again.
 
Just had a quick go before work. Put Afterburner on and un-ticked box.

However, using either GPU as a master didn't seem to make any difference whatsoever. I was seeing the correct voltages and clock speeds when I swapped between the two, but performance was back to being massively under-par.

So looking like I can't use Afterburner for overclocking and monitoring temps. Will have to try Gigabyte OC guru tonight, see if that does the same thing and screws them up.
 
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