CPU-To-GPU Performance Scaling
Much to the chagrin of my boss, I followed up a week of benchmarking with a few days of wading through data, trying to figure out the best way to present these results. We can, for example, consider the cards first.
We clearly see that the Core i7-3770K gets a bigger boost from two Radeon HD 7970s in CrossFire than AMD's FX-8350, but that could just be a general indication of lower CPU performance from the Vishera-based CPU. That is fair enough. The FX is a less expensive processor, so we're completely fine with it not performing as well.
SLI scales a little better than CrossFire on the Intel CPU, and the SLI-versus-CrossFire spread is even wider on the FX-8350-based configuration. We’re getting close to an answer.
Using the Core i7-3770K as a common factor, we find that AMD's Radeon HD 7970 slightly outperforms the GeForce GTX 680 in our test suite. Yet, slightly better scaling allows SLI to catch up to CrossFire.
Conversely, the FX-8350 appears to favor Nvidia's SLI technology over CrossFire. This is just another data point quantifying the potential validity of claims that AMD's cards are more limited on its own processors, and that Nvidia's graphics hardware is able to extract more performance from a top-end FX.
Intel takes an 11% lead over AMD when paired to a single Radeon HD 7970. That lead shrinks to only 9% when a single GeForce GTX 680 is used. Of course, this chart doesn’t make clear whether AMD is favoring the GeForce, or Intel is instead favoring the Radeon.
CrossFire boosts gaming performance on Intel's Core i7-3770K by 72%, but only manages to speed up frame rates on AMD's FX-8350 by 47%. The Vishera-based FX gets a far bigger kick from SLI.