PCI Express 2.0( x16,x16) vs PCi Express 2.0( x8,x8)

I looked up some reviews on this a couple month ago that you can probably find on Google. The general findings are that it will cost you 8% or so on your CrossfireX efficiency (184% vs. 192% if both are 16x). A x4 lane will cost you another 10% or so. I'm just estimating off of memory. But the overall effect is that it doesn't cost you enough to matter much with slower cards (like maybe a 5830 or GTX460).

Top of the line cards though? I can't tell you for certain. You can save money and get 6950's then flash the bios to 6970's. And get a better motherboard that supports two x16 lanes. If you're spending $740 on graphics, you want to get every drop out of it or you might as well be getting dual 5870's--which is what I'd do and save $an extra $250 that I'd spend on a 28" 1920x1200 monitor (although you probably already have a wicked monitor setup).

It's between 1%-2% (16x/16x vs. 8x/8x) depending on the resolution.

A powerful cpu is more important in a high end dual gpu setup than pci-e lanes. What I mean by powerful is 4.5ghz ++

http://www.tomshardware.com/reviews/pcie-geforce-gtx-48...

Dalauder, you need to check your math. 192% eff. is not 8% faster than 184% eff. You don't subtract 184 from 192. LOOL

Baseline is 100% and we're comparing SLI scaling from 100% to 200%. So if it scales 92% worse, then it's still at 100%. If it scales 8% worse, it's at 184%. My math was right from that standpoint. But I guess the question was x16/x16 vs x8/x8 and I was answering x8/x8 & x16/x16 vs. single card. Although crossfire efficiency, which is what I was referencing, only goes from 100% to 200% (except for when it goes outside of that range) and so it was 8% less efficient as a crossfire setup.

So was my math right? Depends on what you think I was trying to say.

Either way the difference between 16x/16x and 8x/8x at normal resolutions is only
1-2%.