Determining the performance gain of SLI/Crossfire

Muriden

So I'm a bit confused on how you determine the performance gain vs cost when considering an SLI/Crossfire set up compared to a single higher model card?

Say the performance difference between two GTX560s compared to a GTX580?

Pirusu

There are various articles on the subject of SLI/Crossfire scaling at Tom's Hardware.

You can also use Anandtech's Bench Tool, to get the performance numbers for different configurations, and get the scaling percentages yourself.

Tom's also has recommended graphics cards every month, and it will often listen two cards as being more cost effective for the performance gains.

rockmonkey

Pirusu wrote: »

There are various articles on the subject of SLI/Crossfire scaling at Tom's Hardware.

You can also use Anandtech's Bench Tool, to get the performance numbers for different configurations, and get the scaling percentages yourself.

Tom's also has recommended graphics cards every month, and it will often listen two cards as being more cost effective for the performance gains.

Pirusu just nailed it all on the head in one simple post that covers all the bases.


I use Tom's Hardware and Anandtech and between the two you can figure out what's the best bang for your buck. I personally prefer to buy a good single card (not cutting edge) that offers great bang for your buck on it's own, and at the same time isn't TOO old, plus has the SLI/Crossfire option. Then in a year if I need more fire power I can pick up a 2nd of that same card for MUCH cheaper and then put them in tandem for a performance boost.

Muriden

I've been using Tom's Hardware but didn't really see a good comparison chart for SLI configs.
The Anandtech benchs are tremendously helpful.

TOGSolid

I'd like to throw out my personal cautionary post:

Do be aware that SLI/Crossfire issues do tend to be one of the more commong things that crop up when a game has any sorta bugginess. Even in games that run fine for most everyone, SLI/Crossfire will still sometimes give you some grief. I kinda prefer the "one really big video card" solution in order to avoid all of that and still get great performance.

Synthesis

I do benchmark tests, as simple as it sounds. Of course, that's very much an "after-the-fact" option. Some games scale much, much better than others....and some cards work much better in pairs than others.

I ended up with SLI because I was already familiar with it (I'd been interested in Crossfire for years beforehand), and I had a motherboard with 3 PCI-Express slots anyway. Unfortunately, I have a case with a really awesome hard drive rack in it that means I can't put in some of the freakishly long high-end models that I was interested in, so SLI with two smaller models was the only option (I barely managed to fit those in too).

TOGSolid

Yeah, those dual GPU cards are massive. I've got a HAF 932 case and even in that a Radeon 5970 is a freakishly big bastard. It's definitely a card you have to plan your build around. If you've got the room for them though, I do recommend em. All the performance of a crossfire/sli setup with none of the glitches that tend to follow them.

Synthesis

None of the same glitches, anyway. Some of the dual GPU cards actually have their own very problematic glitches (I'm most familiar with the Radeons in the 5800 and 5900 series, but it's probably true about Nvidia as well) as well. The least glitchy option, I'm think, would be to get a very high end single chipset (though that might not get you the power you wanted).

Though with a massively huge dual chipset card, you don't have to worry about the SLI/Crossfire Bridge screwing up. I had a bridge go bad, and it caused more than half of games I ran to crash at startup for no apparent reason. Didn't realize it until I turned SLI off, and everything went back to normal.

TOGSolid

Huh, I've never noticed any issues with my 5970 that didn't end up being just general problems that lots of other people had with the game just hating on ATI cards (Metro 2033, I'm looking right at you).

I do plan on stuffing an nvidia card into my rig at some point so that I can use it as a PhysX accelerator via a driver hack, but I need a new mobo first. My trusty ole Asus P6t SE's PCI slots are too close and I don't feel comfortable having another card parked right next to that 5970.

Synthesis

The 5800 x2 and 5900 x2 glitches were reported fairly abundant during the teething process for the cards, and for dual-GPU cards on the whole--particularly for, as you might guess, older games (kind of a repeat of the complaints you'd hear about the 6600GT years ago). If you bought yours a time later, I imagine they would have been ironed out. Aside from a bad SLI Bridge (a fairly obvious hardware problem), I've personally never had any of the famous SLI-related problems, including with the issue of SLI scaling--then again, I'm using an EVGA motherboard with EVGA cards. As always, your experience may vary.

The SLI boost is not always be as high as I'd like depending on the game (for example, it's only about 45% for Shogun 2), but then again, many games don't play well with GeForces or Radeons specifically anyway. I've never had any games slow down from SLI anyway, which is a common complaint when something goes wrong.

TOGSolid

I got my 5970 after the initial rush so that explains that. Funnily enough it had more to do with just waiting for the bastards to get back in stock more than any real desire to wait.

Synthesis

Yeah, I bet the exact same thing happened with the 6600GTs when they first came out....there was a huge rush to snap them up, and thus, a huge body of people to point out all the driver issues and other glitches.

I jumped onto the Fermi wagon a bit late, plus EVGA has a rep for being really anal about putting out driver patches in addition to Nvidia's own (presumably, you could use them with any card of identical make, though EVGA says "DON'T"...), so I've been shockingly glitch free for a 3 - 4 year card shift. All I did was update my drivers.