In referance to a closed tread. about gtx 680

Two 580's in SLi will require more CPU power than a single 680 will simply due to the overhead that SLi introduces, so whilst a newer CPU may give more performance it's not really a fair comparison is it?

While I do know that SLI and crossfire both require more overhead, do have any good links that can show us just how much?

No I don't, sorry.

That would be a good front page article topic.

When you say overhead what do you mean, and what resources are being used to provide this overhead?

The CPU and possibly a little ram.

3DMark Vantage
2 GTX 580 Q9450 4GB memory 3.6GHz
P31497
GPU 28241
CPU 48144
2 GTX 580 i7-950 6GB Memory 4.0GHz
P44583
GPU 40583
CPU 64506
2 GTX 580 i7-3930K 32GB Memory 4.55GHz
P49702
GPU 43341
CPU 88796

Cpu is so important with SLI as I have exeprienced my self too, badad has really highlighted this well, there's not much out there showing this , but an upgade of your cpu in some cases gives your SLI set up a huge leap in performance, mostly with the high end cards in SLI.

Mouse Monkey is right.

Your Using Different Cards (580 vs 680)
Your Using High End SLI as compared to a single card
Your Ram went from 4gb DDR 2 to 6gb DDR3 to 32gb DDR3
Your RAM went from Dual Channel, to Tripple Channel to Quad Channel

to many variables to try and compare them side by side.
a bottlekneck is all about the slowest component holding your system back.

a Single 680 and Q9450 are fairly well matched when it comes to games

add a 2nd one and your going to be fairly limited by ur CPU and the GPU performance will be limited (as you found out with your SLI 580's & Q9450)

A 2500/2600K/SandyBridgeE is far faster than a 680 for games. as you can run multiple 680's and not have them limited by CPU.

If you ran those same bench marks on a SINGLE 580 / 680 you will find the different in results is NOT anywhere near as hugh between CPU config's.

as each solution will be able to run the single card alot closer to its max speeds.

That heavily depends on your resolution. A single 1080p monitor will be CPU limited with those CPU's in a multiple 680 SLI setup in many games, but rarely if ever in a multiple monitor setup.

he is testing with 3DMark Vantage (Performance 1080x1024)

at 1080P a SINGLE 580 or 680 will run every game @ max anyway.

the only reason to run multiple 580's or 680's would be for large resolution gaming / benchmarking

Well if your ever played in 3D in 1920x1080 at max settings or even worst 2560x1600, you'd see why you would need two cards. They also will not play all games at max in a playable frame rate in single card mode. I've been playing in 1920x1080 for years now and don't consider it large resolution and anything above that is.

I know what you mean. Even with a gtx680, I have to turn down settings on all the top end games. The Witcher 2, Metro 2033, and even Skyrim to some degree. Oddly, Crysis 2 with DX11 and texture pack runs smooth with just 1 card, but it looks like it may be using a Virtual 3D mode, similar to how Tridef3d does it.