SLI vs Crossfire…A Comparison
Any serious PC gamer trying to build their own gaming rig should know the difference between SLI and Crossfire and the differences between these two multi-GPU gaming solutions. SLI stands for Scalable Link Interface, and is the multi-GPU solution for NVIDIA video cards that supports up to four NVIDIA video cards that operate in parallel processing. CrossFire refers to the multi-GPU solution for AMD video cards that also supports up to four AMD graphics cards.
Both multi-GPU solutions support from two to four video cards from their respective GPU manufacturers; SLI is exclusive to NVIDIA, while CrossFire is exclusive to AMD video cards. Both multi-GPU solutions will offer performance boosts in terms of raw graphics and computing power, although different drivers and structures of the two types of video cards renders varying amounts of performance boosts. In addition, both SLI and CrossFire have a hybrid option targeted towards systems with on-board video cards, and increases gaming performance by allowing any discrete video cards to operate parallel to the on-board video card, which is often significantly less powerful.
In terms of raw performance differences in graphics output, SLI and CrossFire are very similar when similar generation cards are compared against each other. In almost all cases, the difference in performance comes down to the compatibility of the game with the drivers and structure of the technology instead of a difference in raw power. However, each of these video cards have its distinctive advantages. AMD edges out NVIDIA cards when it comes to overclocking because AMD cards generally have better cooling. Most AMD video cards have 2 or 3 fans installed, which means better overclocking when the limiting factor is cooling. In addition, Eyefinity can be used with AMD CrossFire to support up to 6 screens of different resolutions. Nvidia SLI can only support up to 3 screens, and only when the screens have the same resolution. However, NVIDIA wins out in terms of driver support, as AMD can sometimes be a little late in releasing driver updates for the latest games.
For cards of the same generation, AMD cards are generally 10-20% cheaper than NVIDIA cards. This can be a deciding factor in building budget gaming rigs, while the result for both SLI and CrossFire yields similar performance for the latest games.
In terms of gaming performance, the actual differences in the performance of SLI and CrossFire are highly disputed and fiercely debated. The actual results are often so close and contradictory between multiple sources that it is generally accepted that the raw performance of the two setups, and the differences are usually due to margin of error. For example, the CrossFire setup of two AMD Radeon HD 7950 cards yields a 96% performance boost compared to a single card and even edges out two GeForce GTX 580 cards by about 20 frames per second. However, the same setup loses out to the GeForce GTX 580 SLI setup by the same amount of frames per second in Crysis 2, presumably due to weakness in the CrossFire setup on a DirectX 9 reliant game.