Activision recently released Call of Duty 4: Modern Warfare, the next installment in the popular war game series. Moving away from the World War II setting, Modern Warfare instead centers around a conflict involving Russia and the Middle East. And hey, you even get to die... and then continue the game in the past.

Call of Duty 4 -- For this benchmark we disguise ourselves in the Ghillie suit, load up ACT II - All Ghillied up. Not just for the great gameplay, but also the intense and dense graphics utilized are breathtaking. Massive high-quality texturing, shaders and a serious amount of shadows, fog and debris are applied in this level to mask and hide as best as you can.

Image Quality setting:

• 4x Anti Aliasing
• 16x Anisotropic Filtering
• All settings maxed out

ATI Radeon HD 4870 CrossfireX (2 GPUs - 2 Cards)

4870 CrossfireX -- Quick side note, in all our benchmarks today we'll follow the same chronological order of graphics cards. There is no preference from my side whatsoever. So then, COD4 always has been GPU bound. Therefore I did not expect any big changes in performance, except in high-end 2-way (or more) multi-GPU rendering.

It's clearly the case. But as 10x7 shows you, it's starting to matter. Adding faster cards or more cards is going to show this more clearly. So beware of what you are about this witness, here's where things will turn a little demonic and dark. Are you ready?

ATI Radeon HD 4870 X2 CrossfireX (4 GPUs - 2 Cards)

BAM -- there you go, this is how CPU bound COD4 starts to get when you give it enough GPU power. Obviously when 4 GPUs are crunching numbers, it eats a lot of CPU cycles. I however could not even remotely think it would be this big of a difference. Absolutely shocking to observe. Radeon HD 4870 X2 in CrossfireX folks, with the most stringent set of image quality settings available to us in-game.

Let's see how NVIDIA is doing.

NVIDIA GeForce GTX 260 SLI (2 GPUs - 2 Cards)

With the NVIDIA GTX 260 SLI cards we start to see a really similar pattern. Much like the two 4870's -- anything faster than two GTX 260 in SLI will start showing a CPU bottleneck. But this is nothing though.