Basic SLI Question

[faint545]

When in SLI mode, I know for a fact that this ASUS board will put both cards at x8 speed since that is what it said on the manual, but say that the video cards I get both have 512MB of memory. Will this mean in SLI mode, I will have a total of a x16 card at 1GB of memory?

[Mr.Ferrari]

Not exactly...

Its kinda like the dual core thing. If you have a dual core processor rated at 2ghz, it doesn't mean you combine both numbers to give you 4ghz total. You just have a dual core processor with each core rated at 2ghz.

The two videocards will divide the work and do it independently. The performance of one video card with 1gb memory would not be the same as having two with 512 each. :)

Think of that bridge as way for the cards to share resources. The first fills in one pixel, while the other card fills in another pixel.

[faint545]

So would the performance of a 1GB rated PCIe card perform a little worse than having an SLI 512MB video card since the load is split among two cards instead of having one card take in all the load. Also, my ASUS has two x16 PCIe slots (from what it says) but when I read the manual, the other PCIe slot can only support x8 due to restrictions. My question is what restrictions? Is it ever possible to have two slots that can support a full x16 each? And if a MB can support two x16 slots, does this mean that when in SLI mode, each card will be running at x16?

[Mr.Ferrari]

Now thats very hard to say. I mean you could be comparing 2x7600gt's with 512mb vs. a 8800GTS 340mb and the 8800 would probably win. The amount of memory a card has doesn't factor in to performance (over a certain point) as the processing power of the video card does.

What I mean is, its more reasonable to get one card worth $300, rather then two worth $150 and SLI them. The benefits of SLi are only really reaped once you hit super high resolutions with powerful cards.

Which Asus motherboard are you talking about? Many chipsets just cannot do x16 on both lanes due to design limits, they have a total of 16 lanes to offer no matter what. Others have 32 lanes to offer, therefore its possible.

But keep in mind that the PCI-E X16 bus is very unsaturated. There is very little performance difference between the cards running at X8 or X16.

[faint545]

I have an ASUS M2N-SLI Deluxe (http://www.newegg.com/Product/Product.aspx?Item=N82E16813131013). I'm also planning on getting two EVGA 256-P2-N624-AR (http://www.newegg.com/product/product.asp?item=N82E16814130056) video cards.

Just as a side note, I am some what knowledgeable of video cards, now that I've had some experience with them and when I looked at the specs of that EVGA card, it seemed pretty exceptional to me, meaning it should be able to play most of the high end games on either high settings or max settings. Just for added reinforcement, should this card be able to play most of the high end games on max settings? If not, what should I be looking for in terms of specs.

[Mr.Ferrari]

The resolution you plan to play at has a big part in that. I think most of the newer games you should be fine with max settings as long as your not over ambitious on the resolutions (16x10+). This is just a guess.

Take a look at this review, they use 7900GS in SLI for comparison and benchmark on many games.
http://www.guru3d.com/article/content/377/1/
Skip to page 10 or so to get to the actual testing.

Just a question though, have you already bought one 7900gs? Or are you planning to buy two to begin with?

[faint545]

I haven't bought the 7900GS yet. I'm planning on getting it within the next couple paychecks unless I can find a better one. So far I've bought a Thermaltake Armor case and an ASUS motherboard. My next step is to probably either buy the processor or RAM. Video cards and water cooling system will be the last things I get.

And as far as the resolution goes, my 15.4" screen only allows a max of 1024 x 768 unfortunately.

[Mr.Ferrari]

Thats fine, but truth be told? You would probably notice very little to zero difference with a second 7900GS. What you could do is get one 7900gs right now, and add another down the road if you need the power. As you can see by the benchmarks in that review I posted, even one card has very little problems playing at 1024/768.

Or even better, you could combine the cash you were gonna use for two cards and buy one beast of a card like the 8800GTS 320mb. Have DX10 capability and be future proof.

Its a personal choice, but you honestly don't need two cards for your goals.

[faint545]

Would I be better off getting one card versus an SLI?

I'm always open for new suggestions.

[kmillerusaf]

Like Mr ferrari was saying, I would agree that you are better off saving your money that you were going to shell out for 2 7900GS's and get the 8800GTS 320mb which is best value for buck right now in my opinion in terms of performance, value, and future proofing your sytem. Just my .02 cents

K Mills

[Mr.Ferrari]

Would I be better off getting one card versus an SLI?

I'm always open for new suggestions.

In the long run..yes. If you ever feel the need for even more power in the future, you can always add a second one. Although the 8800GTS will perform at 1024x768 for years before ever needing any more juice :).

[faint545]

I'm looking at the 8800 Ultra Superclocked model of that card and the KO ACS 320MB model. Any opinions on either card? Both are from eVGA.

[Mr.Ferrari]

Well I was combining the total worth of 2 7900gs, for that the 8800GTS 320mb is of ~equivalent price.

The 8800Ultra is a "limited" edition and the performance difference between it and a 8800GTX is the same as if you put a mild overclock on the 8800gtx. Meaning, its not worth it.

Get whatever suits your budget. I personally think the 8800GTS 320Mb is more then enough.

[faint545]

Any large differences between the GTS and the GTX?

[Mr.Ferrari]

More memory, higher clocks, more shaders/stream processors. Its comparable to the step up between a 7900GS to a 7950GT. Nothing that will make too much of a difference unless you have the resolutions to use it.

[faint545]

Just out of curiosity, what's the difference between the Superclocked version and the KO ACS version that causes a $400 difference in price? Besides the fact that the Superclocked runs at a higher clock speed.