How much slower is the I5 vs the I7 in Gaming performance?

With Xfire.

Two setups.

I5 750 @ 4Ghz with 2 4770's in Xfire against a I7 920 @ 4Ghz with 2 4770's in Xfire? How much of a percentage gain would the I7 hold because of the extra lanes?

http://www.tomshardware.com/review [...] ,2379.html

1. How does incorporating 16 lanes of PCI Express 2.0 onto the Lynnfield die affect performance? The answer depends on how many graphics cards you’re using, but is mostly academic with this generation of GPUs. The more pressing concern should be finding a Core i5 that’s fast enough to actually let modern graphics cards stretch their proverbial legs. It all goes back to the concept of building balanced PCs. If you’re going to spend close to a grand on 3D horsepower, you’ll need a heavily-overclocked processor in order to keep pace. With a single Radeon HD 4870 X2, we saw some theoretical advantages to serving all 16 lanes through an on-die controller versus using X58.

2. Will Core i5 handicap you right out of the gate with multi-card configurations? The aforementioned gains evaporated in real-world games, where Core i7’s trended slightly higher, perhaps as a result of Hyper-Threading or its additional memory channel. With two cards installed, Core i5 simply didn’t gain as much performance as Core i7 at high resolutions. It wasn’t, however, noticeably handicapped, and was still able to deliver more performance than Core 2 Quad (also limited to a pair of x8 connections via P45).

3. Are eight lanes per card enough? Almost certainly, yes…in this story. There is a perceivable performance ding associated with halving PCI Express bandwidth when two cards are installed. However, if you flip over to our Core i5 and Core i7 gaming analysis, which tests these two new chips with Turbo Boost turned on, you'll see that in most cases, the higher clocks measured there are able to make up some of the losses at low resolutions, while high-res tests demonstrate very close performance between the mainstream P55 platform and higher-end X58-based configurations.

4. How will P55 compare to X58, P45, and 790GX? Naturally, X58 has an advantage in that it’s able to serve up twin x16 links and communicate with the CPU across a 25 GB/s+ QPI interconnect. P55, P45, and 790GX all force you to split connectivity up unto smaller links if you run multiple graphics cards, though. Integrating that functionality into the processor die looks to be a good thing for Core i5, especially given the motherboard/processor prices we're expecting immediately after launch.

As I've just posted, Lynnfield is limited to only two x8 channels, unlike Bloomfield's dual x16 PCIe channel setup. At least, that's what the Intel guys said.

http://www.tomshardware.com/forum/ [...] ice-change

I was looking for more of an estimated percentage