The Lynnfield Element
Alright, so the gamers shopping for $259 video cards probably aren’t buying $1,000 Core i7-975s (though I still maintain a $279 Core i7-920 overclocked to 4 GHz isn’t out of the question). If you want value-oriented performance from a more affordable Intel-based platform, that means a Core i5/P55 or Core i7/P55 combination.
That also means dividing 16 lanes of PCI Express 2.0 between a pair of cards if you’re running in CrossFire mode. So, our goal here is two-fold.
First, how much effect do those two x8 links have on the performance of a high-performance configuration? We’ll try to answer that one by overclocking a Core i7-870 to 4 GHz and running all of our benchmarks at 1920x1200 with the most demanding settings tested throughout this story. Any significant drops in performance would be indicative of a limitation attributable to the Lynnfield design’s on-die PCI Express controller.
Then, we’ll drop the clock on our i7-870 to 2.93 GHz (with Turbo Boost technology enabled) in order to gauge how a stock-clocked processor would affect gaming performance with two Radeon HD 5850s in CrossFire. By comparing those numbers to the overclocked results, we’ll have a better idea if a CrossFire’d 5850 configuration is overkill for an upper-midrange gaming system, or if you really need a higher-end CPU in order to keep up.
We see some minor variations here, but no performance drops greater than five percent. Given these results, it’d be hard to recommend against a P55 platform simply because of its PCI Express configuration.
Certain games we know are fairly CPU-dependent, like Left 4 Dead and to a lesser extent World in Conflict. It also appears that Resident Evil 5 has a penchant for processing power as we step down from our 4 GHz Core i7-870 to a stock-clocked 2.93 GHz chip. In the situations where the lower-clocked CPU gives up performance, though, you have lots of frame rate already. The most demanding workloads where playability is debatable could still use more GPU muscle.
