Whether AMD or Intel performs better in CrossFire depends on the processors in question and programs you use.
Although AMD owns ATI, the manufacturer of CrossFire, the graphics technology can be used with both AMD and Intel processors. Choosing which CPU you want to use with your ATI graphics cards is largely a matter of preference, but each has a few distinct advantages.
CrossFire, also known as CrossFireX, is a technology created by ATI that enables multi-GPU, or multiple graphics cards on a single computer. Although not perfectly scalable–you won’t reach 100 percent increased performance from having two cards installed over one–there is a measurable increase in performance when implementing multiple GPUs with CrossFire.
Despite AMD owning ATI, AMD processors do not automatically work better with ATI graphics cards. Determining which processor offers better performance in CrossFire is a matter of determining which performs better for the applications you use.
In a benchmark test by AnandTech between the six-core AMD Phenom II X6 and the four-core Intel Core i7 965 Extreme, both rated at 3.2GHz, the Intel processor was a clear leader in most tests. However, the two extra cores of the AMD did give it an edge in some of the testing involving heavily multi-threaded applications, such as Adobe Photoshop. Also, AMD processors tend to be more inexpensive then comparable Intel chips, which is the case in this example.