CrossFire vs. SLI

The other thing we wanted to look at was how CrossFire and SLI scaled across a decent range of games – we plan to look at this in even more detail with more titles at a later date as well, because consistent scaling is of utmost importance when you’re considering a multi-GPU setup.

We included a similar selection of benchmarks to those on the previous page, but we also added an overall performance scaling number, which incorporates every test we ran at said resolution – even those that we have not graphed in order to keep pages at a reasonable length.

One thing that you can expect here is that at lower resolutions, the faster cards are somewhat crippled because they run into CPU limitations quicker than slower cards would at the same resolution and settings. With that in mind, there is nothing wrong with the GeForce GTX 280’s SLI drivers for example, even though it doesn’t scale as well as the dual GeForce GTX 260+ configuration at this resolution – it’s simply running into CPU limitations much quicker with that second card installed.




While the ATI Radeon HD 4870 1GB CrossFire configuration scales much better in some titles, it scales much worse in others based on the data we have obtained here – a lot of that isn't down to CPU limitation and is instead because the drivers aren’t quite as optimised as the Nvidia alternative in some scenarios.

With that in mind then, it looks like Nvidia SLI is the more consistent of the two multi-GPU configurations, even if it doesn’t deliver the most impressive scaling in selected scenarios. The second GeForce GTX 260+ adds more than a 70 percent performance increase on average across the board at 1,680 x 1,050, 1,920 x 1,200 and 2,560 x 1,600 – the same can’t be said for the Radeon HD 4870 1GB CrossFire configuration, but it’s incredibly close to delivering just that at the resolutions listed above.

Of course, all of this doesn’t take the real performance data into account, so we should probably get onto that right away...