SLi or seperate?

[Bligglenuber]

I currently possess a gtx580 and I wanted to upgrade to two in SLi. I know a guy who was selling a gtx580 at a much lower price than a new one.

It turns out the one he was selling has the following specs:

EVGA Classified Edition
Core Clock: 900MHz
Shader clock: 1800Mhz
3GB GDDR5 Ram

whereas my current one is:

Gainward something or other
Core Clock: 783MHz
Shader clock: 1566Mhz
1.5GB GDDR5 Ram

I know that if I were to run the two in SLi the EVGA will be nerfed to match the weaker card. I know that it's possible to run the two cards separately and use the weaker for dedicated physx.

I've already gone ahead and bought the card since it's cheaper than a new gtx580 anyway. My question is, what configuration will net the best performance?

 

[Guest]

Keep the faster card on top and when you need the added power enable the second card.really nothing more to it.thats a nice card by the way if i were getting the gtx 580 thats the one id get..

 

[Bligglenuber]

So running them both in SLI is the most powerful setup then?

 

[chesteracorgi]

Yes SLI is the better option. But get MSI's afterburner software (its freeware) and set the clock to the same frequency. This is necessary to run SLI. BTW you can overclock both of those puppies. Afterburner also has good monitoring tools for temperature and speed.

 

[ubercake]

The tricky thing with SLI is the cards should also have the same amount of memory:

http://www.geforce.com/hardware/technology/sli/faq#c16

Check out the answer to the different memory amounts question 'Can I mix and match graphics cards with different sizes of memory?'.

It may not be the best setup for SLI, but if you can get it too work, this would be the best setup. If you can't get this to function, I would actually sell the gainward 580 and try to pick up another EVGA with the same memory size.

On the other hand, you'd have one heck of a PhysX card in the 580, but few gaming opportunities to use it:

http://www.geforce.com/hardware/technology/physx/pc-games

 

[Bligglenuber]

Okay, thanks for the confirmation that SLI is still the best setup with what I'd have. I've already got afterburner, though I admit I was using it for its monitoring rather than OCing anything. I hope to be able to get the gainward up to the same clockspeeds as the EVGA but I doubt I'll get it any higher. On a related note, any suggestions about cooling the SLI setup? Is it necessary? I know that with my current build the gainward hits 82 degrees as a max temperature (though that's only using 76% of the fan, I leave it on auto. Putting the fan on full it stays at 77 degrees).

EDIT: I took the time to OC the gainward this morning. I got it to a core clock of 900MHz and shader clock of 1800MHz at 1.075V. The temp on it when I'm maxing it out is 90degrees, though I was using the 'Heaven DX11 Benchmark' because furmark throttles the clocks to half of what they should be. I've run a couple games with it like this, though not for any length of time yet, including Crysis2 and BL:R which are some of the most intensive games I have. I've left the fan on auto because having it stay on max the whole time is very noisy. The fact that even when it's at 90degrees the fan is running at about 90% suggests that nvidia considers the temperature to be acceptable.