Help OCing SLI GTX 670's

Avetiso · May 31, 2013

So, I'm crashing after a relatively low OC (+102mhz offset). I'm getting stable 1228mhz on card one and stable 1189mhz on card two. However, I don't know which one is making me crash. I have a suspicion it's card two because GPU-Z registered a 387.0% TDP right before crash. :ouch:

These are reference eVGA GTX 670's, no SC, no FTW. I asked around on Overclock forums, but all I got was 2 replies that didn't answer my question.

Here is my question: To simplify things, can I simply remove one card from my comp? What I want to plan to accomplish is the max overclock on a single card, which should be simpler. I'll write down the stats for the card and mark it as card one (inconspicuously, of course). Then, I'll replace it with the the other card, and do the same. I'll take the one that overclocks the best and insert it as my primary, and the runner-up as secondary. Then I'll turn sync off in Precision-X, and reinsert the values according to the card they correspond to. Things are just too confusing for me, an OC noob, with two cards in there.

I'm following the GTX 670 Master Overclocking Guide over at OCN, but it's not very coherent.

Will this work? (I understand I may still need to make small adjustments after I go back to SLI, but that is already 1-2mhz on the clock type things, I hope)

PSU is 800W Gold-rated, more than enough. CPU @ stock, 3570k.
Case is HAF 922 with good airflow, about to get better.

This will also give me something to do until my new Corsair SP120's HP come in to help me keep these damn things under 70C. :fou:

Also, it has been well established that the slowest card does NOT limit the faster one for the GTX 600 series.

Kraszmyl · May 31, 2013

You cant set independent oc profiles for each gpu in sli. It ill always clock both cards to the same level as the lowest preforming card. Also with how NVidia designed the 6xx cards youre honestly better off just letting boost do its thing because if you set the boost offset to high you run the risk of the cards underclocking themselves as well.

Your general idea of overclocking the cards alone to find their peaks is mostly correct. Also keep in mind depending on your cooling and psu having only a single card vs two running can change your stable overclock as well. I typically just overclock them together, its easier all around.

Edit

Noticed you mentioned you know that the cards don't have to be matched? Honestly never heard of that and I had to oc my evga gtx680 to match my gigabyte one because it was dragging it down to the evgas clocks. I guess ill play with that in the morning.

But the advice of leaving the boost alone or pairing them still stands. If you set it to high and the clocks on both cards wildly fluctuate I cant imagine that is good for the sli stability.

Avetiso · May 31, 2013

Kraszmyl :

This is not true. Kepler boost is different and set in stone between every single card produced. I just ran Heaven at stock clocks and both GPU-Z and Precision-X performance logs confirm that the cards ran at different speeds throughout the tests. At stock clocks, card one ran a constant 1137mhz and card two ran at 1097mhz. When OC'd, the same is true, again. Kepler boost is defined from the factory, so if you walk into Fry's and buy 2 GTX 670's right now, exact same kind, odds are they will run at different speeds, just like mine do. That's because their Kepler boost are set from factory, and is different for each GPU.

Also, I can monitor the speeds, so I will know if they are being throttled, and I will tone down by boost. But odds are, I'll crash instead of that.

10hellfire01 · May 31, 2013

That has always been a method, do it by one card at a time. You're perfectly fine doing this, if anything it has always been suggested to do this to find which card is the one that overclock less, generally speaking.

The PSU being 800w and gold rated...yeah it's important but isn't the whole story. What also matters is the PSU component quality and how many amps it sens out on the +12 V rails. I'm assuming you have a single rail PSU with higher amperage or a multi rail PSU.

This is an easy read since I'm horrible at typing on my phone

http://www.tomshardware.com/forum/335793-28-rail-question I'm assuming you're fine off to begin with. To find the amperage for your +12 V rail(s) you can google the model/make, or check out the box/manual it came with.

Avetiso · May 31, 2013

10hellfire01 :

Thank you for your input. Looking at the box (it's a Cooler Master Silent Pro Gold 800W) it says 12V : 65A. It is a single-rail PSU. Newegg says the same. Should I be fine? I'm not running any clocks on my 3570k.

Avetiso · May 31, 2013

Kraszmyl :

Accidentally deleted my first reply to you.

I see your edit.

Both cards will run at different speeds even at stock settings. This just confuses me sometimes, but I'm coping. I can upload some graphs for you to see what I mean, if you want.

10hellfire01 · May 31, 2013

Yeah you're prefect--doesn't hurt to make sure.

The easiest way of doing this is removing one card at a time. However, since the cards don't necessarily have to be synchronized, you can do it while they're both in, just one at a time until you notice something happening. As long as you're raising the cV of the GPU as you go about it...well that's really all you can do.

You should keep in mind that all components, as much as they appear the same, have small differences/imperfections in them. You may never actually be able to reach as high a clock for the 2nd card. You also have plenty of wattage, you're maybe hitting ~550 W max in SLI + other components.

As you probably know the symptoms of a...mediocre overclock is that of the driver crashing, and seeing white snow (pixels) in 3D applications. So if your clocks are too high regardless, you should see some of this. I used Crysis when I got this card in 2010,it being demanding and vibrant allowed me to see snow easier. If a slightly higher voltage doesn't ease it then you're too high for the card to handle. As you saw in the guide, due to Boosts dynamic nature you have to pick a good spot for the power target. Too high and you will see the card throttle down its clocks more often; I think the guy in your guide said it was 70 c this usually occurs. It's a lot of trial and error

Compared to normal overclocking, you literally need to find a middeground for each portion to play nicely. As I see it, its trying to maximize what you can get when trying to stay away from 70 C degrees. So maybe you can loosen the power target a bit to see if the card is still stable, etc. It's possible as a new timer yourself you could be going a bit heavy with the target (not saying, just guessing).

Avetiso · May 31, 2013

10hellfire01 :

Yeah you're prefect--doesn't hurt to make sure.

The easiest way of doing this is removing one card at a time. However, since the cards don't necessarily have to be synchronized, you can do it while they're both in, just one at a time until you notice something happening. As long as you're raising the cV of the GPU as you go about it...well that's really all you can do.

You should keep in mind that all components, as much as they appear the same, have small differences/imperfections in them. You may never actually be able to reach as high a clock for the 2nd card. You also have plenty of wattage, you're maybe hitting ~550 W max in SLI + other components.

As you probably know the symptoms of a...mediocre overclock is that of the driver crashing, and seeing white snow (pixels) in 3D applications. So if your clocks are too high regardless, you should see some of this. I used Crysis when I got this card in 2010,it being demanding and vibrant allowed me to see snow easier. If a slightly higher voltage doesn't ease it then you're too high for the card to handle. As you saw in the guide, due to Boosts dynamic nature you have to pick a good spot for the power target. Too high and you will see the card throttle down its clocks more often; I think the guy in your guide said it was 70 c this usually occurs. It's a lot of trial and error

Compared to normal overclocking, you literally need to find a middeground for each portion to play nicely. As I see it, its trying to maximize what you can get when trying to stay away from 70 C degrees. So maybe you can loosen the power target a bit to see if the card is still stable, etc. It's possible as a new timer yourself you could be going a bit heavy with the target (not saying, just guessing).

Well, I am maxed at 122% at all times, like the guide says to be. I will try playing with it. Thanks for the great info, you have been very helpful. I appreciate it.

10hellfire01 · May 31, 2013

No problem. I was full of questions when I started a long time ago too. As much of a pain in the *** GPU Boost may seem to be, it does work. Or at least others have shown it works well most of the time.

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Help OCing SLI GTX 670's

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