Is my PSU bottlenecking my Msi GTX 660TI OC PE edition

[snorex1]

Hi everyone, I recently purchased 2 msi gtx 660ti oc pe edition. they come stock with a overlocked 1019 core. I tested out 1 card with over clocking on msi afterburner and i was able to reach 150+ core and about 450+ on men with a core voltage set at +100 mem voltage +50 and aux at +20, also tweaked the fan graph a bit. but when i put in my second card it got unstable and i couldn't reach anywhere close to my over clocks on 1 card. now I'm set at +50 core voltage and +20 mem and +10 aux. my over clock on sli is +80 core and +350 on mem. anyone know whats bottlenecking my over clocked sli build? I'm thinking its because of my psi because i was reading that over clocked sli requires more than 750w psu. Any information would help i will list my build below.

motherboard : asus crosshair v
Cpu : fx-8120 oc'ed 4.2ghz
rams : 16gb of corsair vengeance 1333mhz
psu : rosewill capstone 750w 80+ gold

side note-my gpu's stay at a cool 60-65 degrees under full load. and this was tested with msi kombuster and 3d mark 11 extreme on loop for 2 hours.

 

[DJDeCiBeL]

The PSU is fine (especially that one). You would be pulling maybe 650W with everything (CPU and both GPU's) OC'd to the absolute max, and everything running at a full 100% load (never happens, anyway, unless you make it happen by stress testing the CPU AND GPU's at the same time). Even if it was closer to 750W, that PSU is great, and can provide a full 750W continuous (I have one, I know). If that system ever pulled more than 750W, I would be extremely surprised and flabbergasted.

Also, if the system was trying to pull more than 750W, the system would just shut down. It would not affect overclocking headroom.

From what I've seen, 2 cards in SLI never reach the same clocks as a single card when OC'ing. I don't know why that is, but it seems to be the case.

 

[giovanni86]

Probably not too much help, but i remember trying to do that with my two 9800GTX's in sli and they did not OC higher in a pair. I've heard that it really depends, i think you can push 1 card further by itself then having two in SLI but thats what i heard. As for power that seems good enough, doubt that its your PSU.

 

[snorex1]

thanks for the replays, i figured that it could be because the cards are in sli. but reason i thought it was because of my psu was because my computer restarted not because it crashed or anything, it just blank screened and rebooted itself and this was while i was stressing the gpu's in sli. i was thinking this isn't a normal reboot from oc failure.

 

[DJDeCiBeL]

but reason i thought it was because of my psu was because my computer restarted not because it crashed or anything, it just blank screened and rebooted itself and this was while i was stressing the gpu's in sli. i was thinking this isn't a normal reboot from oc failure.

That's happened to me with a single card (and I know my system doesn't pull anywhere near 750W). For me, it was just because it was an unstable OC (tried 1Ghz with my 560 but even with max volts, it couldn't do it, just froze the system/black screened).

 

[DJDeCiBeL]

If the system didn't totally shut down and you had to turn off and unplug the PSU to reset it, then it's not the PSU.

 

[snorex1]

That's happened to me with a single card (and I know my system doesn't pull anywhere near 750W). For me, it was just because it was an unstable OC (tried 1Ghz with my 560 but even with max volts, it couldn't do it, just froze the system/black screened).

even if the power turned off on my rig? because the power turned off for a good 2 second and it booted itself back up. isn't that because of power failure?

 

[DJDeCiBeL]

even if the power turned off on my rig? because the power turned off for a good 2 second and it booted itself back up. isn't that because of power failure?

Read my last reply, but as long as it restarted normally, it's not the PSU. If it was the PSU, it would have totally shut down and not been able to restart, and you would have had to manually reset it, by turning it off and unplugging it.

 

[DJDeCiBeL]

Also, just to show how little power the 6xx cards pull, have a look at this:

As you can see, SLI 660 Ti's pull much less than 750W, and overclocking them isn't going to make up the 400W difference.

 

[snorex1]

Read my last reply, but as long as it restarted normally, it's not the PSU. If it was the PSU, it would have totally shut down and not been able to restart, and you would have had to manually reset it, by turning it off and unplugging it.

thats also something I've noticed after putting in my second card, whenever i switched off the power and switched it back on manually on the back of my psi, the lights on my motherboard would light up( on a single card) now that i put my second card in, the lights do not light up anymore, i have to power on my rig to spark it up.

 

[DJDeCiBeL]

thats also something I've noticed after putting in my second card, whenever i switched off the power and switched it back on manually on the back of my psi, the lights on my motherboard would light up( on a single card) now that i put my second card in, the lights do not light up anymore, i have to power on my rig to spark it up.

Eh, that's a bit odd, and I honestly have no idea why it would do that, but that sounds more like a motherboard issue (since it does power up).

 

[DJDeCiBeL]

Also, it seems like you're convinced that it's the PSU, lol, and I'm not sure I'm getting through to you.

If you want to get a PSU with more wattage, knock yourself out, you're more than welcome to, but I can promise you that it won't "solve" the overclocking problem. All you're experiencing is the cards not liking what you're trying to do to them.

 

[snorex1]

Also, it seems like you're convinced that it's the PSU, lol, and I'm not sure I'm getting through to you.

If you want to get a PSU with more wattage, knock yourself out, you're more than welcome to, but I can promise you that it won't "solve" the overclocking problem. All you're experiencing is the cards not liking what you're trying to do to them.

hmm atm im a little convinced about my psu barely being able to power up my build, only cause i have a set of radeon 6870 on the side to test this out, i swapped out the 2 cards with the 6870 and the lights on my motherboard goes on just fine as i switch the psu back on, but as soon as i swap it back to my gtx 660ti the lights isn't coming on anymore. I do however appreciate your input in this tho. but I'm just a little confused as to why it would do that. at the moment, to me it looks like the gtx 660ti is pushing the psi to its edge and its barely having enough power to run my setup. what are your thoughts about this test?

 

[snorex1]

also ignore why it always says psi instead of psu, the autocorrect on this mac is annoying me.

 

[DJDeCiBeL]

Could be the 6870's only being PCIe 2.0 while the 660 Ti's are 3.0 (which again, would point to a motherboard problem).

The 6870's and 660 Ti's should pull around the same amount of wattage (maybe even a little less for the 660 Ti's). The 6xx cards just barely sip power. They're not huge, monstrous power hogs. If anything, it should have had trouble with the 6870's, if wattage was an issue.

 

[snorex1]

hmm that could be a possibility, however I was thinking about purchasing a psu from a local store and test it out, only because i could always return the item if it is indeed not the psu. anyhow, thanks for the help and i am pretty convinced it isn't my psu either. but who knows, doesn't hurt to try i guess

 

[snorex1]

Best answer selected by snorex1.

 

[snorex1]

hmm so i did confirm something.. either my power supply is defective or the load is too much for my psu. last night as i was playing games i started smelling a weird burning smell from my computer, and this actually has been happening ever since i put the second card into my cpu build. whenever i stress test or have the gpus under load, i started smelling a weird plastic burning smell. Last night i heard a pop from my rig then i quickly looked and there was 3 more pops and sparks flying out the back of my psu vents. so i took everything out and tested the psu with a pin and some fans to see if it was still giving out power. looks like the psu still has juice to power up the fans but it wouldn't power up my rig anymore.
on the side note.. i did order a 1250w ocz zx power supply and it is arriving tomorrow. I'm just hoping the psu didn't take any other parts out along with it.. -_-

 

[DJDeCiBeL]

Oh man, that sucks, but I'm guessing that it was just a faulty PSU to begin with. 750W is more than enough for the SLI 660 Ti's, like I said.

As it is, you're WAY overpowered with that 1250W unit, and you could do quad SLI now, if you wanted to, lol.

 

[snorex1]

Oh man, that sucks, but I'm guessing that it was just a faulty PSU to begin with. 750W is more than enough for the SLI 660 Ti's, like I said.

As it is, you're WAY overpowered with that 1250W unit, and you could do quad SLI now, if you wanted to, lol.

lol yeah i figured im overkilling but i rather be on the safe side. and it was on sale so i couldn't help it but to make sure I'm not pushing the psu too hard. any who i RMA'ed the psu and ill probably just sell the replacement one or keep it on the side incase the 1250 decides to go faulty on me.