re: PC Discussion - Gaming, Performance and Enthusiasts

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How does it work having more than one video card?

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you and Finch...

Finch is wanting to crossfire a week after he builds and you are asking before you have even built.

Welcome to the money pit!

These goddamn videos and websites and whatever else are like crack, man. I feel that I've entered into dangerous territory.

Does 3-way crossfire ready mean I can have three video cards at once? For frick's sake

What sort of stuff do you need multiple video cards to handle? Is it just with multiple monitors or are there other benefits? I have a budget build and it can handle stuff like Bioshock Infinite on pretty much max settings.

That's basically what I was getting at. Once I decide to step up to 1440p (after a lot more learning), I'll be working on crossfiring and whatnot. Until then, just learn and enjoy it what I'll do.

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I have a budget build and it can handle stuff like Bioshock Infinite on pretty much max settings.

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You have a 6300 with a Sapphire 7870 if I recall? You should be fine for a while too at 1080p.

You can still OC to get a little more but I bet you are pushing 6k+ or so on 3D Mark11.

Speaking of...I want to fool with 3D Mark today and see what I am running with everything at stock.

I'm just getting antsy. I'm a very proactive guy and I like to have things that I may need before I need them. Until I play a game and see how it operates, I won't know if my specs are legit or not. Obviously they are, but I don't know that yet.

For AMD cards, it's called crossfiring, and for nVidia cards it's called SLI.

Ideally, in crossfire/SLI you would add the same card (e.g., if you had a 7950 and wanted to crossfire, you'd add another 7950). You can crossfire a weaker card with a stronger card of the same performance class (say, a 7970 with a 7950), but it would be bottlenecked by the 7950 effectively turning the setup into crossfired 7950s.

Adding a second video card to your setup (and connecting the two cards via a crossfire or SLI bridge) combines the power of the two GPUs. But it's not as simple as saying it doubles the performance. In games that support it well, you'll see a performance increase of "almost" double vs one card. Maybe 75-90%. Some games which aren't optimized for a multi-GPU setup might not use the second card to its full potential, or not at all. Some games won't scale the GPUs properly (e.g., it might use 40% of each GPU). But today's games and drivers are much better at supporting it. You only occasionally encounter a game that doesn't support crossfire very well, and that's often solvable with third party software (at least for AMD cards).

SLI/Crossfire doesn't double your memory, either, as each card only has access to its own memory, and the cards essentially work in tandem. This isn't that big of an issue -- two 1GB 6950s will still significantly outperform a single 2GB 6950.

It's taken a long time, but I think crossfire/SLI is becoming more of a viable solution for cost-effective graphics performance. Newer games are making better use of it, and drivers are optimizing it even more and fixing past issues such as frame latency.

You can crossfire/SLI up to 4 cards, but you see serious diminishing returns when you use more than 2 cards. You have to consider the platform you're using. Mainstream platforms like socket 1155/1150 have a limited number of PCI-E lanes that really only provides optimal support for 2 cards. You can certainly get a performance boost by adding a third, but it's a much smaller increase due to a combination of things, such as driver optimization and PCI-E saturation. There are some 1155/1150 motherboards with PLX chips that offer a "synthetic" increase in PCI-E bandwidth by prioritizing lanes on the fly, but it's still not going to make the most optimal use of a third or fourth card.

True story: I was browsing 3mark11 scores earlier last month just to make sure my e-peen is still the biggest. Because of my overclocks, I have the highest score of all 3dmark11 systems that are running the same CPU/GPU combo (4770k and 2 x 7970s). Out of curiosity, I started looking at haswell systems that are running 3 7970s. My two overclocked 7970s were actually beating scores from people running 3 of them at stock on a haswell system, or else I was within 1-5% of their score. I've always been of the opinion that if you think you need a third video card, you bought the wrong card to begin with.

I like it when you talk dirty to me like that.

That just gave me wood